Crazy sailor’s taking boat on road (6)
I believe the answer is:
absurd
'crazy' is the definition.
(I've seen this in another clue)
'sailor's taking boat on road' is the wordplay.
'sailor's' becomes 'ab's' (abbreviation for able seaman).
'taking' is a charade indicator (letters next to each other).
'boat' becomes 'u'.
'on' says to put letters next to each other.
'road' becomes 'rd' (abbreviation).
'abs'+'u'+'rd'='ABSURD'
(Other definitions for absurd that I've seen before include "word to describe Beckett's theatre!" , "'Derisory, cockeyed (6)'" , "Highly illogical" , "Derisory, preposterous" , "Ridiculous, quite nonsensical" .)