An excessive number? (5)
I believe the answer is:
gross
This clue is a double definition.
'an excessive' is the first definition.
(thesaurus)
'number?' is the second definition.
(gross is a kind of number)
(Other definitions for gross that I've seen before include "large total before deductions" , "Not refined, vulgar like 12 dozen" , "clearly wrong" , "144 - vulgar - bloated - before tax" , "Earn" .)