Husband in great pain (4)
I believe the answer is:
ache
'pain' is the definition.
(ache is a kind of pain)
'husband in great' is the wordplay.
'husband' becomes 'h'.
'in' indicates putting letters inside.
'great' becomes 'ace' (I've seen this before).
'h' placed into 'ace' is 'ACHE'.
(Other definitions for ache that I've seen before include "Feel sore" , "Dull throbbing pain" , "Long ? pain" , "Persistent dull pain" , "Throb - hurt" .)