In Gap, love to fill in, displaying creativity (9)
I believe the answer is:
invention
'displaying creativity' is the definition.
(I've seen this before)
'in gap love to fill in' is the wordplay.
'gap' becomes 'vent' (vent is a kind of gap**).
'love' becomes 'o' (In tennis, 'love' means 'zero').
'to fill' indicates putting letters inside.
'o' put inside 'in' is 'ion'.
'in'+'vent'+'ion'='INVENTION'
(Other definitions for invention that I've seen before include "Something newly conceived" , "Creation of a device or new process" , "Offspring of necessity" , "of necessity, a child?" , "Creation of something new" .)