Tired before plugging art director (9)
I believe the answer is:
knackered
'tired' is the definition.
'before plugging art director' is the wordplay.
'before' becomes 'ere' (poetic term for 'before').
'plugging' is an insertion indicator (I've seen this in other clues).
'art' becomes 'knack' (I can't explain this - if you can you should give a lot more credence to this answer).
'director' becomes 'd' (abbreviation eg in film reviews).
'knack'+'d'='knackd'
'ere' put into 'knackd' is 'KNACKERED'.
Can you help me to learn more?
(Other definitions for knackered that I've seen before include "Worn out" , "Exhausted (slang)" .)