Grab young offender on ship (7)
I believe the answer is:
impress
'grab' is the definition.
(thesaurus)
'young offender on ship' is the wordplay.
'young offender' becomes 'imp' (I've seen this in other clues).
'on' becomes 're' ('on' can be mean 'with reference to').
'ship' becomes 'ss'.
'imp'+'re'+'ss'='IMPRESS'
(Other definitions for impress that I've seen before include "look big?" , "Mark made by a seal or stamp" , "Have profound effect upon" , "Mark of a stamp/seal" , "produce a profound effect" .)