Crackers are able to expand (9)
I believe the answer is:
elaborate
'expand' is the definition.
(I know that expand can be written as elaborate)
'crackers are able to' is the wordplay.
'crackers' indicates anagramming the letters (informal term for mad).
'are'+'able'+'to'='areableto'
'areableto' is an anagram of 'ELABORATE'.
(Other definitions for elaborate that I've seen before include "flesh out?" , "With many parts or details, maybe a pattern" , "Develop in more detail" , "Detailed, complicated" , "Ostentatious, possibly" .)