Planned key medical after school (7)
I believe the answer is:
schemed
'planned' is the definition.
(I've seen this before)
'key medical after school' is the wordplay.
'key' becomes 'e' (I've seen this in other clues**).
'medical' becomes 'med' (common abbreviation).
'after' means one lot of letters go next to another.
'school' becomes 'sch'.
'e'+'med'='emed'
'emed' put after 'sch' is 'SCHEMED'.
(Other definitions for schemed that I've seen before include "contrived" , "Intrigued" , "Conspired" , "Devised plans" , "Cooked up" .)