Submission of plea involving Queen (9)
I believe the answer is:
deference
'submission' is the definition.
(I've seen this before)
'plea involving queen' is the wordplay.
'plea' becomes 'defence' (as in a legal defence).
'involving' is an insertion indicator.
'queen' becomes 'er' (abbreviation for Elizabeth Regina).
'defence' placed around 'er' is 'DEFERENCE'.
'of' acts as a link.
(Other definitions for deference that I've seen before include "honour" , "show respect" , "Compliance with another's wishes, polite respect" , "Reed fence? (anag)" , "Submission to will of another" .)