A child's resting place (5)
I believe the answer is:
perch
'resting place' is the definition.
(I've seen this before)
'a child's' is the wordplay.
'a' becomes 'per' (eg 'one a day' means 'one per day').
'child' becomes 'ch' (abbreviation for child).
'per'+'ch'='PERCH'
(Other definitions for perch that I've seen before include "Roost; old measure" , "Bird's resting place or old measure of length" , "pew?" , "Rod on which bird roosts" , "Settle" .)