Look after Liberal in den (4)
I believe the answer is:
lair
'den' is the definition.
(I know that den can be written as lair)
'look after liberal' is the wordplay.
'look' becomes 'air' (I've seen this before).
'after' says to put letters next to each other.
'liberal' becomes 'l' (abbreviation).
'air' put after 'l' is 'LAIR'.
'in' acts as a link.
(Other definitions for lair that I've seen before include "Waylay" , "mire where he lives" , "Place of seclusion (informal)" , "Earth" , "Hiding place, den" .)