Fish made captain lose head (6)
I believe the answer is:
kipper
'fish' is the definition.
(type of fish)
'captain lose head' is the wordplay.
'captain' becomes 'skipper' ('skipper' can be a synonym of 'captain').
'lose head' means to remove the first letter.
'skipper' with its initial letter taken off is 'KIPPER'.
'made' is the link.
(Other definitions for kipper that I've seen before include "being in bed?" , "(Fishy) type of tie" , "Cured fish (one having forty winks?)" , "part of breakfast?" , "Dried and smoked herring" .)