Marxist revolutionary and British head of state in lift (5)
I believe the answer is:
cheer
'lift' is the definition.
(lift can mean to cheer up)
'marxist revolutionary and british head of state' is the wordplay.
'marxist revolutionary' becomes 'Che' (Che Guevara).
'and' is a charade indicator (letters next to each other).
'british head of state' becomes 'ER' (short for Elizabeth Regina, ie Queen Elizabeth).
'che'+'er'='CHEER'
'in' is the link.
(Other definitions for cheer that I've seen before include "Fare" , "Applaud; mood" , "pair of hips can get me going!" , "Shout applause and support" , "Cry of approval" .)