Sober sailor sent to collect money (9)
I believe the answer is:
abstinent
'sober' is the definition.
(similar in meaning)
'sailor sent to collect money' is the wordplay.
'sailor' becomes 'ab' (abbreviation for able seaman).
'to collect' means one lot of letters goes inside another (inserted letters are collected by others).
'money' becomes 'tin' (old-fashioned slang term for money).
'sent' placed around 'tin' is 'stinent'.
'ab'+'stinent'='ABSTINENT'
(Other definitions for abstinent that I've seen before include "Not indulging appetite for food or drink" , "Refusing alcohol" , "self-restraint" , "Avoiding alcohol" , "Keeping off alcohol" .)