Spends too much on account of extra writing taking a year (8)
I believe the answer is:
overpays
'spends' is the definition.
The answer and definition can be both to do with ownership as well as being verbs in their -s form.
Perhaps they are linked in a way I don't understand?
'too much on account of extra writing taking a year' is the wordplay.
'too much' becomes 'over' (over can mean to too great an extent).
'on' is a charade indicator (letters next to each other) (in a down clue, letters appear on others).
'account of extra writing' becomes 'ps' (I can't justify this - if you can you should believe this answer much more).
'taking' indicates putting letters inside.
'year' becomes 'y'.
'a'+'y'='ay'
'ps' placed around 'ay' is 'pays'.
'over'+'pays'='OVERPAYS'
Can you help me to learn more?
(Other definitions for overpays that I've seen before include "Lays out more money than something's worth" , "Rewards too highly" .)