King collared by parsimonious consort with whom words are often exchanged (8,7)
I believe the answer is:
sparring partner
'with whom words are often exchanged' is the definition.
'king collared by parsimonious consort' is the wordplay.
'king' becomes 'r' (r is abbreviation for rex).
'collared by' indicates putting letters inside (I've seen this in other clues).
'parsimonious' becomes 'sparing'.
'consort' becomes 'partner' ('partner' can be a synonym of 'consort'**).
'r' inserted within 'sparing' is 'sparring'.
'sparring'+'partner'='SPARRING PARTNER'
(Other definitions for sparring partner that I've seen before include "What a boxer needs" , "whose attacks are helpful, in practice?" , "Ring mate" , "hits rehearsed with me?" , "Boxer's opponent during training" .)