Queen involved in enigmatic opera that's more impenetrable (7)
I believe the answer is:
opaquer
'more impenetrable' is the definition.
Both the definition and answer are comparative adjectives. Perhaps you can see a link between them that I can't see?
'queen involved in enigmatic opera' is the wordplay.
'queen' becomes 'qu' (abbreviation for queen).
'involved in' is an insertion indicator.
'enigmatic' is an anagram indicator (a puzzling form of the letters).
'opera' with letters rearranged gives 'opaer'.
'qu' inserted within 'opaer' is 'OPAQUER'.
'that's' acts as a link.
Can you help me to learn more?
(Other definitions for opaquer that I've seen before include "Less transparent" , "Rather obscure" , "Less clear" , "It's not so easy to grasp" .)