Happy? Not terribly, though in the money (7)
I believe the answer is:
content
'happy?' is the definition.
(associated in meaning)
'not terribly though in the money' is the wordplay.
I cannot really understand how this works, but
an anagram of 'not' is 'ont' which is present in the answer.
'the' could be 't' (the is pronounced as a 't' sound in some dialects) and 't' is present in the answer.
'money' could be 'c' and 'c' is found within the answer.
The remaining letters 'en' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for content that I've seen before include "Gist" , "Satisfied; volume" , "Satisfied, happy enough" , "substance of book?" , "Elements" .)