Leader of Oxford Group keeping church cat (6)
I believe the answer is:
ocelot
'cat' is the definition.
(ocelot is a kind of cat)
'leader of oxford group keeping church' is the wordplay.
'leader of' indicates taking the first letters.
'group' becomes 'lot'.
'keeping' indicates putting letters inside.
'church' becomes 'CE' (abbreviation for Church of England).
The initial letter of 'oxford' is 'o'.
'o'+'lot'='olot'
'olot' placed around 'ce' is 'OCELOT'.
(Other definitions for ocelot that I've seen before include "Striped and spotted wildcat" , "American wild cat" , "Wild cat of the Americas" , "Small leopardlike cat" , "Spotted New World feline" .)