"Heavens", the scamp put in "it's not big enough!" (6)

I believe the answer is:
skimpy
'not big enough' is the definition.
Both the definition and answer are adjectives. Maybe you can see an association between them that I can't see?
'heavens the scamp put in' is the wordplay.
'heavens' becomes 'sky' (sky is a kind of heavens).
'the scamp' becomes 'imp' ('imp' can be a synonym of 'scamp').
'put in' means one lot of letters goes inside another.
'sky' placed around 'imp' is 'SKIMPY'.
'it's' is the link.
Can you help me to learn more?
(Other definitions for skimpy that I've seen before include "Inadequate (of clothing)" , "Meagre; (of clothes) short and revealing" , "Made with barely sufficient material (of clothes)" , "Scanty or mean" , "Having hardly enough" .)
