Offer to buy includes red-top parrot, maybe (4)
I believe the answer is:
bird
'parrot maybe' is the definition.
(I know that parrot is a type of bird)
'offer to buy includes red-top' is the wordplay.
'offer to buy' becomes 'bid' (I've seen this in another clue).
'includes' indicates putting letters inside.
'red-top' becomes 'r' (top of the word 'red-').
'bid' enclosing 'r' is 'BIRD'.
(Other definitions for bird that I've seen before include "Creature - time in prison" , "Flier - spell in prison" , "chat, perhaps?" , "Member of class Aves" , "Dawn chorus etc - book by Sebastian Faulks" .)