Dictator back in charge is a monster (5)
I believe the answer is:
troll
'monster' is the definition.
(I know that troll is a type of mythical creature)
'dictator back in charge' is the wordplay.
'back' indicates one should take the final letters.
'in' indicates putting letters inside.
'charge' becomes 'toll' (toll is a kind of charge).
The last letter of 'dictator' is 'r'.
'r' put inside 'toll' is 'TROLL'.
'is a' acts as a link.
(Other definitions for troll that I've seen before include "unwanted contributor to site?" , "Fairytale monster" , "Ugly Norse dwarf" , "Try to catch fish" , "Scandinavian monster" .)