Overtake father by boat (4)
I believe the answer is:
pass
'overtake' is the definition.
(synonyms)
'father by boat' is the wordplay.
'father' becomes 'pa' (pa is a kind of father).
'by' is a charade indicator (letters next to each other).
'boat' becomes 'ss'.
'pa'+'ss'='PASS'
(Other definitions for pass that I've seen before include "Cross-mountain route; permit" , "Elapse; mountain route" , "Graduate, perhaps? A" , "sticky situation if one is pretty" , "Authorise; overtake" .)