Stern and bow incorporating heart of ship (6)
I believe the answer is:
behind
'stern' is the definition.
(synonyms)
'bow incorporating heart of ship' is the wordplay.
'bow' becomes 'bend' (I've seen this in another clue).
'incorporating' indicates putting letters inside.
'heart of' says to take the centre.
The middle letters of 'ship' are 'hi'.
'bend' going around 'hi' is 'BEHIND'.
'and' is the link.
(Other definitions for behind that I've seen before include "in van? No" , "Following - late" , "Serving time" , "Hidden by; bottom" , "Seat" .)