Cocktail ingredient right for man to swallow (5)
I believe the answer is:
prawn
'cocktail ingredient' is the definition.
(I've seen this before)
'right for man to swallow' is the wordplay.
'right' becomes 'R' (common abbreviation).
'for' is a charade indicator (letters next to each other) (I've seen this in other clues).
'man' becomes 'p' (abbreviation for pawn, a chess piece or 'man').
'to swallow' becomes 'awn' (I can't justify this - if you can you should give a lot more credence to this answer).
'r' after 'p' is 'pr'.
'pr'+'awn'='PRAWN'
(Other definitions for prawn that I've seen before include "Small, edible crustacean" , "Shrimp-like crustacean" , "basis for cocktail" , "Marine crustacean" , "Large shrimp" .)