Clever sort rounded hill covering wide area (4-3)
I believe the answer is:
know-all
'clever sort' is the definition.
(clever person)
'rounded hill covering wide area' is the wordplay.
'rounded hill' becomes 'knoll' (I've seen this in another clue).
'covering' indicates putting letters inside.
'wide' becomes 'w' (abbreviation e.g. in cricket).
'area' becomes 'a' (maths abbreviation).
'w'+'a'='wa'
'knoll' placed around 'wa' is 'KNOW-ALL'.
(Other definitions for know-all that I've seen before include "Clever clogs!" , "Self-styled polymath" , "One supposedly omniscient" , "Person who thinks he has all the answers" , "Clever dick!" .)