Spring upon moving edges of cape (6)
I believe the answer is:
pounce
'spring' is the definition.
(pounce is a kind of spring)
'upon moving edges of cape' is the wordplay.
'moving' is an anagram indicator.
'edges of' means to remove the middle letters.
'cape' with its centre taken out is 'ce'.
'upon' is an anagram of 'poun'.
'poun'+'ce'='POUNCE'
(Other definitions for pounce that I've seen before include "Spring or swoop down on to attack" , "Jump swiftly on, as cat might" , "(Of cat) sudden leap to seize prey" , "Jump down on suddenly" , "Spring (on prey like a cat)" .)