One's not satisfied with English in Roman assembly (6)
I believe the answer is:
moaner
'one's not satisfied' is the definition.
I can't judge whether this defines the answer.
'english in roman assembly' is the wordplay.
'english' becomes 'E' (abbreviation).
'in' means one lot of letters goes inside another.
'assembly' is an anagram indicator.
'roman' anagrammed gives 'moanr'.
'e' inserted inside 'moanr' is 'MOANER'.
'with' is the link.
Can you help me to learn more?
(Other definitions for moaner that I've seen before include "Grouch" , "One who complains" , "Complainer" , "Grumbler" .)