Ship entering sound in difficulty (6)
I believe the answer is:
hassle
'difficulty' is the definition.
(I've seen this in another clue)
'ship entering sound' is the wordplay.
'ship' becomes 'SS' (prefix in ship names eg SS Great Britain).
'entering' indicates putting letters inside.
'sound' becomes 'hale' (both can mean healthy).
'ss' going inside 'hale' is 'HASSLE'.
'in' is the link.
(Other definitions for hassle that I've seen before include "Hound" , "Colloquial harassment or annoyance" , "Informally, annoyance or quarrel" , "Modern word for bother and annoyance" , "problem" .)