Former partner virtuous accepting huge revelation (8)
I believe the answer is:
exposure
'revelation' is the definition.
(I know that exposure is a type of revelation)
'former partner virtuous accepting huge' is the wordplay.
'former partner' becomes 'ex' (an ex-partner).
'virtuous' becomes 'pure' (synonyms).
'accepting' means one lot of letters goes inside another (inserted letters are accepted).
'huge' becomes 'os' (abbreviation for outsize).
'pure' enclosing 'os' is 'posure'.
'ex'+'posure'='EXPOSURE'
(Other definitions for exposure that I've seen before include "that is brought to light?" , "Lack of cover" , "being unmasked" , "Publicity, or state of being revealed" , "Risk for Antarctic explorer" .)