The end of spinnaker in large sailing ship (4)
I believe the answer is:
brig
'sailing ship' is the definition.
(brig is a kind of sailing ship)
'the end of spinnaker in large' is the wordplay.
'the end of' indicates one should take the final letters.
'in' means one lot of letters goes inside another.
'large' becomes 'big' ('big' can be a synonym of 'large'**).
The last letter of 'spinnaker' is 'r'.
'r' inserted into 'big' is 'BRIG'.
(Other definitions for brig that I've seen before include "Two-masted square-rigger" , "senior officer briefly used" , "Two-masted square-rigged sailing ship" , "Two-master; army officer (abbr.)" , "A ship; army officer (abbr.)" .)