London theatre sounding unimportant and not revolutionary (9)
I believe the answer is:
lyttelton
'london theatre sounding unimportant' is the definition.
I know nothing about this answer so I can't judge whether it can be defined by this definition.
'not revolutionary' is the wordplay.
I cannot quite understand how this works, but
an anagram of 'not' is 'ton' which is present in the answer.
This explanation may well be incorrect...
'and' is the link.
Can you help me to learn more?
(Other definitions for lyttelton that I've seen before include "'Humph', English jazz musician and broadcaster, d. 2008" , "Trumpeter - national theatre" .)