Signify average (4)
I believe the answer is:
mean
This clue is a double definition.
'signify' is the first definition.
('mean' can be a synonym of 'signify')
'average' is the second definition.
(type of average)
(Other definitions for mean that I've seen before include "mercenary" , "Despicable" , "Stingy; Scrooge-like" , "Name for being tight-fisted" , "Stingy in average way" .)