1 under 100 could be 99 (4)
I believe the answer is:
cone
'be 99' is the definition.
(99 Flake is an ice cream product with a cone)
'1 under 100' is the wordplay.
'o' becomes 'one' ('one' can be a synonym of '1'**).
'under' means one lot of letters go next to another.
'o00' becomes 'c' (roman numeral).
'one' after 'c' is 'CONE'.
'could' is the link.
(Other definitions for cone that I've seen before include "often full of ice" , "Road furniture!" , "Motorway menace" , "Volcano peak" , "may obstruct lane" .)