Compare Liberal president with nationalist leader (5)
I believe the answer is:
liken
'compare' is the definition.
('liken' can be a synonym of 'compare')
'liberal president with nationalist leader' is the wordplay.
'liberal' becomes 'l' (abbreviation).
'president' becomes 'ike' (I've seen this before**).
'with' means one lot of letters go next to another.
'leader' suggests taking the first letters.
The first letter of 'nationalist' is 'n'.
'l'+'ike'+'n'='LIKEN'
(Other definitions for liken that I've seen before include "Point out the resemblance (to)" , "Compare" , "Equate" , "Represent as similar" .)