Crime ending in disaster, stopping a child (5)
I believe the answer is:
arson
'crime' is the definition.
(crime of illegally starting a fire)
'ending in disaster stopping a child' is the wordplay.
'ending in' suggests the final letters.
'stopping' is an insertion indicator (inserted letters stop or plug a gap).
'child' becomes 'son' (male child).
The final letter of 'disaster' is 'r'.
'a'+'son'='ason'
'r' placed into 'ason' is 'ARSON'.
(Other definitions for arson that I've seen before include "It may get you in court" , "Torching" , "Crime of fire setting" , "Illegally firing" , "matchplay, say?" .)