Sailor straightened nets out (6)
I believe the answer is:
absent
'out' is the definition.
(similar in meaning)
'sailor straightened nets' is the wordplay.
'sailor' becomes 'ab' (abbreviation for able seaman).
'straightened' indicates anagramming the letters (I've seen 'straighten' mean this).
'nets' is an anagram of 'sent'.
'ab'+'sent'='ABSENT'
(Other definitions for absent that I've seen before include "Forgetful, with mind on other things" , "nowhere to be seen" , "Missing, lacking" , "Not attending" , "Not present or focused" .)