Let down by an inferior editor (7)
I believe the answer is:
lowered
'let down' is the definition.
(I've seen this in another clue)
'an inferior editor' is the wordplay.
'an inferior' becomes 'lower' (I've seen this before).
'editor' becomes 'ed' (abbreviation).
'lower'+'ed'='LOWERED'
'by' acts as a link.
(Other definitions for lowered that I've seen before include "Let down gently" , "Moved something down" , "Threatened" , "looked sullen" , "Brought down" .)