Mary's painting unusual insect (7,6)
I believe the answer is:
praying mantis
'insect' is the definition.
(praying mantis is a kind of insect)
'mary's painting unusual' is the wordplay.
'unusual' indicates anagramming the letters.
'marys'+'painting'='maryspainting'
'maryspainting' with letters rearranged gives 'PRAYING MANTIS'.
(Other definitions for praying mantis that I've seen before include "Small creature" , "Large carnivorous insect" , "Pagan ministry (anag.)" , "Grasping creature" , "Predatory insect" .)