Tricky angle on outside of easel (6)
I believe the answer is:
elfish
'tricky' is the definition.
(I've seen this before)
'angle on outside of easel' is the wordplay.
'angle' becomes 'fish' (synonyms).
'on' says to put letters next to each other.
'outside of' says to hollow out the word (remove centre letters).
'easel' with its centre taken out is 'el'.
'fish' after 'el' is 'ELFISH'.
(Other definitions for elfish that I've seen before include "Mischievous" , "Tricky" .)