Unwrapping small pouch is a pain (4)
I believe the answer is:
ache
'is a pain' is the definition.
(I've seen this before)
'unwrapping small pouch' is the wordplay.
'unwrapping' means to look at the middle letters (letters which 'wrap' the word are removed).
'pouch' becomes 'che' (I can't explain this - if you can you should believe this answer much more).
The central letter of 'small' is 'a'.
'a'+'che'='ACHE'
Can you help me to learn more?
(Other definitions for ache that I've seen before include "Dull prolonged pain" , "Cause pain" , "Long ? pain" , "Persistent dull pain" , "Continuous hurt" .)