Excluded lawless conceptualist who had pocketed pencil. (7)
I believe the answer is:
outcast
'conceptualist who had pocketed pencil' is the definition.
The definition suggests a singular noun which matches the answer.
'excluded lawless' is the wordplay.
'excluded' becomes 'out' (I've seen this in another clue).
'lawless' becomes 'cast' (I can't justify this - if you can you should give a lot more credence to this answer).
'out'+'cast'='OUTCAST'
Can you help me to learn more?
(Other definitions for outcast that I've seen before include "'Person excluded from society, a pariah (7)'" , "One excluded from group" , "Derelict" , "Exile" , "one sent to Coventry" .)