Tear my school trousers (6)
I believe the answer is:
scorch
'tear' is the definition.
(thesaurus)
'my school trousers' is the wordplay.
'my' becomes 'cor' (I've seen this in other clues**).
'school' becomes 'sch'.
'trousers' is an insertion indicator (to trouser can mean to contain or hold).
'cor' inserted within 'sch' is 'SCORCH'.
(Other definitions for scorch that I've seen before include "Burn on surface, char" , "Become burnt on the surface" , "Singe" , "Burn; drive very fast (informal)" , "Shrivel through heat" .)