Employ pundit, regardless of pressure (5)
I believe the answer is:
exert
'employ' is the definition.
(eg exerting strength is using or employing it)
'pundit regardless of pressure' is the wordplay.
'pundit' becomes 'expert' (a pundit is an expert on a particular topic).
'regardless of' suggests deleting specific letters.
'pressure' becomes 'p' (abbreviation).
'expert' with 'p' taken out is 'EXERT'.
(Other definitions for exert that I've seen before include "Bring into use, say strength" , "Bring into use, strength or influence" , "Work strenuously" , "Bring to bear, perhaps influence" , "Bring into play, wield" .)