General disorder? That's swell (7)
I believe the answer is:
enlarge
'swell' is the definition.
(swell can mean to get bigger)
'general disorder?' is the wordplay.
'disorder?' indicates anagramming the letters (a disordered version of the letters).
'general' anagrammed gives 'ENLARGE'.
'that's' acts as a link.
(Other definitions for enlarge that I've seen before include "Wax" , "Describe in more detail" , "Make greater" , "Gleaner (anag.)" , "Expand" .)