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 there's an association between them I don't understand?
'problem raised by editor' is the wordplay.
'problem' becomes 'sum' (as in a mathematical problem).
'raised by' says the letters should be written in reverse.
'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" .)