I am apt to be cheeky (11)
I believe the answer is:
impertinent
'cheeky' is the definition.
(thesaurus)
'i am apt' is the wordplay.
'i am' becomes 'im'.
'apt' becomes 'pertinent' ('pertinent' can be a synonym of 'apt').
'im'+'pertinent'='IMPERTINENT'
'to be' acts as a link.
(Other definitions for impertinent that I've seen before include "Rude" , "Showing little respect" , "of no relevance" , "Bold" , "Disrespectful" .)