Accross

1 Reversal (turning) of TED (of which Kennedy is an example) contains (embrace) sibling (SIS) = DESIST (stop),

4 Double definition of STREAMER,

9 English (ENG) contained in (using … during) Roman reception (AVE) = AVENGE (retaliate for),

10 Exchange (SUB) + messages (TEXTS) = SUBTEXTS (ones that aren’t explicit),

12 Double definition of TURNOVER,

13 Anagram (crooked) of SPIRE containing (stuck with) unfavourable aspect (N) = SNIPER (assailant),

15 Anagram (criminal) of HELD GATHER IT = LIGHT-HEARTED (not serious),

18 Party (RECEPTION) + initially (Ist) = RECEPTIONIST (someone who welcomes,

21 Homophone (allegedly) of receive report (hear/HERE OF) = HEREOF (concerning this),

22 At home (IN) + journalist (ED) + initial letters (starts to) of words 6-9 = INEDIBLE (off),

24 Homophone (rumour) of abundant (lush/LUSC) + debts (IOUS) = LUSCIOUS (inviting),

25 RAS (of which surrealists are an example) follow (latch on to) absurd (MAD) = MADRAS (material),

26 Cryptic definition of MANX CATS,

27 If read 2,4 or 6 double definition of BEHEAD.

Down

1 Anagram (drastic) of ISOLATED = DIASTOLE (enlargement of the heart),

2 Become really angry (RAGE) follows 1st letter (beginning to) of (S)how + support (TEE) = STEERAGE (old word for basic accommodation),

3 Cryptic definition of SIGN OF THE ZODIAC (made by Ford),

5 (T)ime + away (OUT) = TOUT (recommend),

6 Anagram of (confused) of TEEN + TEEN (doubly) surrounding (about) wholehearted (CORDIAL) = ENTENTE CORDIALE (agreement),

7 Politicians (MPS) contain (claiming) 1st letters (to begin with) of words 6-8 = MIX-UPS (mistakes),

8 Double definition of RESORT, 11 Hand over (REFER) + both sides of(E)videnc(E) = REFEREE (middleman),

14 PaREnt minus (wants) A+(N)ew+(T)ime followed by look after (TEND) = PRETEND (kid),

16 Anagram (new) of USER’S BID = DISBURSE (pay out), 17 Reversal (returning) of sweets (DESSERTS) = STRESSED (caused concerned),

19 Outside letters (empty) of (S)howroo(M) contains (assumes) auro (HALO) = SHALOM (peace),

20 Answer is hidden in (features) maORI SONg = ORISON (prayer),

23 Work (RUN) supported by 1st letter (leader) of (T)ories = RUNT (the least viable).