Huge rises count to a great extent (6)
I believe the answer is:
sorely
'to a great extent' is the definition.
Both the answer and definition are adverbs. Perhaps you can see an association between them that I can't see?
'huge rises count' is the wordplay.
'huge' becomes 'os' (abbreviation for outsize).
'rises' shows that the letters should be reversed in order.
'count' becomes 'rely' (I've seen this in another clue).
'os' written backwards gives 'so'.
'so'+'rely'='SORELY'
Can you help me to learn more?
(Other definitions for sorely that I've seen before include "Painfully" , "Acutely; very much" , "Extremely, severely" .)