Post over on one side (7)
I believe the answer is:
upright
'post' is the definition.
(I've seen this before)
'over on one side' is the wordplay.
'over' becomes 'up' (e.g. if your time is up it is over).
'on' says to put letters next to each other.
'one side' becomes 'right' (I've seen this before).
'up'+'right'='UPRIGHT'
(Other definitions for upright that I've seen before include "honestly" , "Honest (like a piano?)" , "extremely reliable?" , "Vertical like rugby goal post" , "Moral" .)