Dull scenes essentially fronted by principal actor (6)

I believe the answer is:
leaden
'dull' is the definition.
(I've seen this before)
'scenes essentially fronted by principal actor' is the wordplay.
I cannot really understand how this works, but
'principal' could be 'lead' (synonyms) and 'lead' is present in the answer.
The remaining letters 'en' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for leaden that I've seen before include "Heavy - plodding" , "Depressing - heavy" , "Leaned over in slow, heavy way" , "Oppressive" , "Gloomy - slow-moving" .)
