Grumble after collecting books in a state (7)
I believe the answer is:
montana
'state' is the definition.
(Montana is an example)
'grumble after collecting books in a' is the wordplay.
'grumble' becomes 'moan' (I've seen this before).
'after collecting' indicates putting letters inside.
'books in' becomes 'nt' (New Testament. I am not sure about the 'in' bit.).
'moan' placed around 'nt' is 'montan'.
'montan'+'a'='MONTANA'
Can you help me to learn more?
(Other definitions for montana that I've seen before include "State of NW USA" , "Nato man (anag) - US state" , "Send manna to this US state" , "The "Big Sky State"" , "North-west US state bordering Canada" .)