Bank clerk is cold and comparatively grey (7)
I believe the answer is:
cashier
'bank clerk' is the definition.
(synonyms)
'cold and comparatively grey' is the wordplay.
'cold' becomes 'c' (eg on taps).
'and' is a charade indicator (letters next to each other).
'comparatively grey' becomes 'ashier' ('ashy' can be similar in meaning to 'grey').
'c'+'ashier'='CASHIER'
'is' is the link.
(Other definitions for cashier that I've seen before include "Drum out of the army" , "One handling money" , "person dealing in LSD, say, once?" , "may be a shop-worker" , "Bank worker - dismiss from the armed forces" .)