Number diving into Italian river, extremely choppy, might (7)
I believe the answer is:
potency
'might' is the definition.
(I've seen this before)
'number diving into italian river extremely choppy' is the wordplay.
'number' becomes 'ten' (ten is a kind of whole number).
'diving into' indicates putting letters inside.
'italian river' becomes 'po'.
'extremely' says to hollow out the word (remove centre letters).
'choppy' with its centre taken out is 'cy'.
'po'+'cy'='pocy'
'ten' placed within 'pocy' is 'POTENCY'.
(Other definitions for potency that I've seen before include "Might" , "Capacity" , "Great power" , "Power; pet cony (anag.)" , "authority" .)