An unusual term I deserve (5)
I believe the answer is:
merit
'deserve' is the definition.
(I know that deserve can be written as merit)
'an unusual term i' is the wordplay.
'an unusual' indicates anagramming the letters.
'term'+'i'='termi'
'termi' anagrammed gives 'MERIT'.
(Other definitions for merit that I've seen before include "Excellence that deserves to be honoured" , "Good point or quality" , "of a high order?" , "Have a right" , "Deserve or warrant" .)