Maybe regular but not uniform, being bigger (6)
I believe the answer is:
larger
'bigger' is the definition.
('large' can be a synonym of 'big')
'maybe regular but not uniform' is the wordplay.
'maybe' indicates an anagram.
'but not' is a deletion indicator.
'uniform' becomes 'u' (phonetic alphabet: alpha, bravo, charlie etc.).
'regular' with 'u' taken away is 'reglar'.
'reglar' with letters rearranged gives 'LARGER'.
'being' is the link.
(Other definitions for larger that I've seen before include "Comparatively bigger" , "Greater in size" , "Ebullient person may be describes as ?? than life" , "bigger,greater" , "Comparatively big" .)