Flexible English carry on in charge (7)
I believe the answer is:
'flexible' is the definition.
(I know that flexible can be written as elastic)
'english carry on in charge' is the wordplay.
'english' becomes 'e' (abbreviation).
'carry on' becomes 'last'.
'in charge' becomes 'ic' (abbreviation for 'in charge').
(Other definitions for elastic that I've seen before include "Able to stretch" , "Stretch material" , "Flexible (material)" , "Variable" , "'Flexible, springy (7)'" .)