Free when the reel is broken by the rough sea (7)
I believe the answer is:
release
'free' is the definition.
(to release someone is to free them)
'the reel is broken by the rough sea' is the wordplay.
'is broken by' indicates anagramming the letters (a broken form of the letters).
'the rough' indicates an anagram (a rough or broken ordering of the letters).
'reel' with letters rearranged gives 'rele'.
'sea' anagrammed gives 'ase'.
'rele'+'ase'='RELEASE'
'when' is the link.
(Other definitions for release that I've seen before include "Free - delivery" , "Liberate" , "Let go" , "put out" , "loose" .)