Pretentious editor subject to influence (8)
I believe the answer is:
affected
'pretentious' is the definition.
(I've seen this before)
'editor subject to influence' is the wordplay.
'editor subject' becomes 'ed' (I can't justify this - if you can you should give a lot more credence to this answer).
'to' means one lot of letters go next to another (I've seen this in other clues).
'influence' becomes 'affect' (I've seen this before).
'ed' put after 'affect' is 'AFFECTED'.
Can you help me to learn more?
(Other definitions for affected that I've seen before include "in a pretentious way" , "Influenced or touched by an external factor" , "Deeply moved" , "False - unnatural" , "Pretended; artificial" .)