English politician has level that's comparatively vacuous (7)
I believe the answer is:
emptier
'comparatively vacuous' is the definition.
('empty' can be a synonym of 'vacuous')
'english politician has level' is the wordplay.
'english' becomes 'e' (abbreviation).
'politician' becomes 'mp'.
'has' is a charade indicator (letters next to each other).
'level' becomes 'tier' (I've seen this before).
'e'+'mp'+'tier'='EMPTIER'
'that's' acts as a link.
(Other definitions for emptier that I've seen before include "More vacuous" , "Being more hungry" , "more in need of food" , "Containing less" , "I'm Peter (anag)" .)