One look may be child's-play (1-3)
I believe the answer is:
i-spy
'be child's-play' is the definition.
I can't tell whether this definition defines the answer.
'one look' is the wordplay.
I cannot really understand how this works, but
'one' could be 'i' (Roman numeral) and 'i' is present in the answer.
'look' could be 'spy' (spy can mean to look or see) and 'spy' is found in the answer.
No letters remain.
This explanation may well be incorrect...
'may' acts as a link.
Can you help me to learn more?
(Other definitions for i-spy that I've seen before include ". ... with my little eye (children's game)" , "Wordgame" , "Child's guessing game" , "Game played with young children" , "Child's game: ''. ... with my little eye'" .)