Intervenes, seeing pace wrong (5,2)
I believe the answer is:
steps in
'intervenes' is the definition.
('step in' can be a synonym of 'intervene')
'pace wrong' is the wordplay.
'pace' becomes 'step' ('step' can be a synonym of 'pace').
'wrong' becomes 'sin' (I've seen this before).
'step'+'sin'='STEPS IN'
'seeing' is the link.
(Other definitions for steps in that I've seen before include "Takes over" , "Intervenes" .)