Question marks (3)
I believe the answer is:
ifs
'question marks' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for ifs that I've seen before include "No ...,ands or buts, no argument allowed" , "Suppositions, may be accompanied by buts" , "Conditions or suppositions, may join with buts" , "If . . . and ands were pots and pans" , "Conditional conjunctions" .)