Sanctify head of banking? Not so much (5)
I believe the answer is:
bless
'sanctify' is the definition.
(synonyms)
'head of banking? not so much' is the wordplay.
'head of' says to take the initial letters.
'not so much' becomes 'less' (I've seen this before).
The first letter of 'banking' is 'b'.
'b'+'less'='BLESS'
(Other definitions for bless that I've seen before include "Wish happiness" , "Give honour to" , "Give benediction" , "Anoint" , "Call God's favour upon" .)