Rocky, having struck bow in tilt — narrow vessel (5,4)
I believe the answer is:
canal boat
'narrow vessel' is the definition.
(I've seen this before)
'rocky having struck bow in tilt' is the wordplay.
'rocky' becomes 'Balboa' (Rocky Balboa from the Rocky films).
'having struck bow' means to remove the first letter (the front or bow of the word is removed).
'in' indicates putting letters inside.
'tilt' becomes 'cant' (synonyms).
'balboa' with its first letter taken off is 'alboa'.
'alboa' put within 'cant' is 'CANAL-BOAT'.
(Other definitions for canal boat that I've seen before include "Inland waterway vessel" , "craft?" , "Narrow vessel" , "One may tour Venice" , "Waterways vessel" .)