Sailor straying? That’s peculiar (8)
I believe the answer is:
aberrant
'peculiar' is the definition.
(thesaurus)
'sailor straying?' is the wordplay.
'sailor' becomes 'ab' (abbreviation for able seaman).
'straying?' becomes 'errant' (I've seen this in another clue).
'ab'+'errant'='ABERRANT'
'that's' acts as a link.
(Other definitions for aberrant that I've seen before include "Wandering, straying" , "'Deviant, behaviour say (8)'" , "departing from standards" , "rogue" , "Deviating from the norm, at barren state" .)