Is for more than one? (3)
I believe the answer is:
are
'is for more than one?' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for are that I've seen before include "Era (anag.)" , "Is, in the plural" , "Unit of land measure equal to 100 square metres" , "(We/you/they) exist" , "(They/you/we) exist" .)