Jokes about RI volunteers and prudes (8)
I believe the answer is:
puritans
'prudes' is the definition.
('puritan' can be a synonym of 'prude')
'jokes about ri volunteers' is the wordplay.
'jokes' becomes 'puns' (punning is a kind of joking).
'about' indicates putting letters inside.
'volunteers' becomes 'TA' (abbreviation for Territorial Army).
'ri'+'ta'='rita'
'puns' enclosing 'rita' is 'PURITANS'.
'and' is the link.
(Other definitions for puritans that I've seen before include "Stern religious people like Rasputin" , "Strictly religious people like Rasputin" , "Killjoys, prudes" .)