Contemplate dime wasted on gallery (8)
I believe the answer is:
meditate
'contemplate' is the definition.
(I know that contemplate can be written as meditate)
'dime wasted on gallery' is the wordplay.
'wasted' indicates anagramming the letters.
'on' is a charade indicator (letters next to each other) (in a down clue, letters appear on others).
'gallery' becomes 'tate' (Tate Modern, Tate Britain etc).
'dime' with letters rearranged gives 'medi'.
'medi'+'tate'='MEDITATE'
(Other definitions for meditate that I've seen before include "Relax mentally" , "Muse" , "Engage in contemplation" , "Ruminate" , "Ponder" .)