Sailor to unravel and let off the hook (7)
I believe the answer is:
absolve
'let off the hook' is the definition.
(I've seen this before)
'sailor to unravel' is the wordplay.
'sailor' becomes 'ab' (abbreviation for able seaman).
'to unravel' becomes 'solve' (I've seen this in another clue).
'ab'+'solve'='ABSOLVE'
'and' is the link.
(Other definitions for absolve that I've seen before include "Declare (someone) free of guilt" , "Clear of blame or guilt" , "Grant pardon for" , "Exonerate" , "Let off the hook" .)