Extension incorporated front of roof with ease (8)
I believe the answer is:
increase
'extension' is the definition.
(thesaurus)
'incorporated front of roof with ease' is the wordplay.
'incorporated' becomes 'inc'.
'front of' says to take the initial letters.
'with' is a charade indicator (letters next to each other).
The initial letter of 'roof' is 'r'.
'inc'+'r'+'ease'='INCREASE'
(Other definitions for increase that I've seen before include "Make larger in a sincere way" , "Make (amount) greater" , "Become greater in number" , "Grow, expand" , "step up" .)