Idiot caught in hill (5)
I believe the answer is:
dunce
'idiot' is the definition.
(I know that dunce is a type of idiot)
'caught in hill' is the wordplay.
'caught' becomes 'c' (cricket abbreviation).
'in' indicates putting letters inside.
'hill' becomes 'dune' (I have seen 'Hill of sand ' mean 'dune' so perhaps 'hill' could also mean 'dune').
'c' inserted within 'dune' is 'DUNCE'.
(Other definitions for dunce that I've seen before include "Term of ridicule applied to followers of John Duns Scotus" , "An ignoramus" , "Stupid man!" , "Term of ridicule for John Dun Scotus followers" , "Dolt" .)