Considered problem raised by editor (5)
I believe the answer is:
mused
'considered' is the definition.
The answer and definition can be both related to thinking as well as being past participle verbs.
Maybe they are linked in a way I don't understand?
'problem raised by editor' is the wordplay.
'problem' becomes 'sum' (arithmetic problem).
'raised by' shows that the letters should be reversed in order.
'editor' becomes 'ed' (abbreviation).
'sum' reversed gives 'mus'.
'mus'+'ed'='MUSED'
Can you help me to learn more?
(Other definitions for mused that I've seen before include "Fuddled" , "Closer" , "Reflected or pondered" , "'Meditated, mulled (5)'" , "Contemplated" .)