Standard covers one or two (4)
I believe the answer is:
pair
'two' is the definition.
(pair is a kind of two)
'standard covers one' is the wordplay.
'standard' becomes 'par' (I've seen this before).
'covers' is an insertion indicator.
'one' becomes 'i' (Roman numeral).
'par' enclosing 'i' is 'PAIR'.
'or' acts as a link.
(Other definitions for pair that I've seen before include "item" , "Twosome" , "Brace, couple" , "flight of stairs" , "Agreement to avoid division" .)