Consultant initially against deploying face mask (7)
I believe the answer is:
advisor
'consultant' is the definition.
(I know that consultant can be written as advisor)
'initially against deploying face mask' is the wordplay.
'initially' suggests taking the first letters.
'face mask' becomes 'visor' (mask for one's face).
The initial letters of 'against deploying' is 'ad'.
'ad'+'visor'='ADVISOR'
(Other definitions for advisor that I've seen before include "One recommends" , "consultant" , "Assistant" , "Guide; VI roads (anag.)" , "one counsels" .)