"If ___ I had known!" (4)
I believe the answer is:
only
(Other definitions for only that I've seen before include "Except that; single" , "Mere" , "Solely, lone" , "Solely; except that" , "Simply" .)
I believe the answer is:
only
(Other definitions for only that I've seen before include "Except that; single" , "Mere" , "Solely, lone" , "Solely; except that" , "Simply" .)