Clergyman heartless but smart (4)
I believe the answer is:
cute
'smart' is the definition.
(I've seen this before)
'clergyman heartless' is the wordplay.
'clergyman' becomes 'curate' (curate is a kind of clergyman).
'heartless' means to remove the middle letters.
'curate' with its centre removed is 'CUTE'.
'but' acts as a link.
(Other definitions for cute that I've seen before include "Lovable" , "Location" , "Small and attractive - cunning" , "Fly" , "Daintily pleasing" .)