Keen on turning in? No good chanting (8)
I believe the answer is:
intoning
'chanting' is the definition.
('intone' can be a synonym of 'chant')
'keen on turning in? no good' is the wordplay.
'keen on' becomes 'into' (I've seen this before).
'turning' is a reversal indicator.
'no' becomes 'n' (common abbreviation).
'good' becomes 'g' (abbreviation).
'in' back-to-front is 'ni'.
'into'+'ni'+'n'+'g'='INTONING'
(Other definitions for intoning that I've seen before include "Reciting with a flat voice" , "Reciting like a chant" , "Chanting" .)