Smooth leader of people finally meeting monarch (7)
I believe the answer is:
plaster
'smooth' is the definition.
(thesaurus)
'leader of people finally meeting monarch' is the wordplay.
'leader of' indicates taking the first letters.
'finally' becomes 'last' ('last' can be a synonym of 'finally'**).
'meeting' is a charade indicator (letters next to each other).
'monarch' becomes 'er' (abbreviation for Elizabeth Regina).
The initial letter of 'people' is 'p'.
'p'+'last'+'er'='PLASTER'
(Other definitions for plaster that I've seen before include "Stuff that sticks on ceilings or wounds" , "Medical dressing" , "One to cover wall, wound" , "First-aid item" , "Stucco" .)