Want Mark to face Manchester, say (8)
I believe the answer is:
scarcity
'want' is the definition.
(I've seen this before)
'mark to face manchester say' is the wordplay.
'mark' becomes 'scar' ('scar' can be a synonym of 'mark').
'to face' is a charade indicator (letters next to each other).
'manchester say' becomes 'city' (manchester is a kind of city).
'scar'+'city'='SCARCITY'
(Other definitions for scarcity that I've seen before include "Shortage" , "Something uncommon" , "Poverty" , "Lack - dearth" , "Shortness of supply" .)