Second smoked herring for captain (7)
I believe the answer is:
skipper
'captain' is the definition.
('skipper' can be a synonym of 'captain')
'second smoked herring' is the wordplay.
'second' becomes 's' (common abbreviation).
'smoked herring' becomes 'kipper' (I've seen this before).
's'+'kipper'='SKIPPER'
'for' is the link.
(Other definitions for skipper that I've seen before include "being in charge?" , "who makes short hops" , "girl with rope?" , "Shakespeare's giddy youth" , "Captain - small butterfly - fish" .)