Hardly a mark on the side of the face (6)
I believe the answer is:
scarce
'hardly' is the definition.
('scarce' can be a synonym of 'hardly')
'a mark on the side of the face' is the wordplay.
'a mark on' becomes 'scar' (I am not sure about this - if you are sure you should believe this answer much more).
'the side of' means to remove the middle letters (I've seen 'sides of' mean this (only the letters on the sides remain)).
'the face' becomes 'coalface' (coalface is a kind of face).
'coalface' with its middle removed is 'ce'.
'scar'+'ce'='SCARCE'
Can you help me to learn more?
(Other definitions for scarce that I've seen before include "Like gold dust" , "Not plentiful, hard to find" , "Scant, meagre" , "Hard to get" , "Common? Definitely not" .)