The master initially served smoked herring (7)
I believe the answer is:
skipper
'the master' is the definition.
('skipper' can be a synonym of 'master')
'initially served smoked herring' is the wordplay.
'initially' suggests taking the first letters.
'smoked herring' becomes 'kipper' (I've seen this before).
The first letter of 'served' is 's'.
's'+'kipper'='SKIPPER'
(Other definitions for skipper that I've seen before include "who makes short hops" , "One who misses" , "Chap aboard trawler" , "Shakespeare's giddy youth" , "Captain - one using a rope" .)