Uncompromising person getting difficult on ship (9)
I believe the answer is:
hardliner
'uncompromising person' is the definition.
(I've seen this before)
'difficult on ship' is the wordplay.
'difficult' becomes 'hard' (synonyms).
'on' means one lot of letters go next to another.
'ship' becomes 'liner' (liner is a kind of ship).
'hard'+'liner'='HARDLINER'
'getting' is the link.
(Other definitions for hardliner that I've seen before include "Doctrinaire type" , "man of principle" , "Uncompromising advocate" , "politician" , "One's rigorous in application" .)