Clever chap supporting Turkey? Or a fool? (9)
I believe the answer is:
birdbrain
'a fool?' is the definition.
(I've seen this before)
'clever chap supporting turkey?' is the wordplay.
'clever chap' becomes 'brain' (brain can mean a brainy person).
'supporting' means one lot of letters go next to another (in a down clue, some letters go below others).
'turkey?' becomes 'bird' (turkey is a kind of bird).
'brain' after 'bird' is 'BIRDBRAIN'.
'or' is the link.
(Other definitions for birdbrain that I've seen before include "Twittering twit?" , "Silly person (with sparrow's mind?)" , "Stupid" , "Fool" .)