Where one may be prone to interrupting play (5)
I believe the answer is:
futon
'where one may be prone' is the definition.
Although both the answer and definition are singular nouns, I can't understand how one could define the other.
'to interrupting play' is the wordplay.
'interrupting' is an insertion indicator.
'play' becomes 'fun' (synonyms).
'to' going into 'fun' is 'FUTON'.
Can you help me to learn more?
(Other definitions for futon that I've seen before include "Foldable mattress" , "Type of sofa bed" , "Japanese mattress with frame, a bed-couch" , "Unsprung roll-up mattress" , "Japanese mattress with wooden frame used as bed" .)