Move at home to intervene (4,2)
I believe the answer is:
step in
'intervene' is the definition.
('step in' can be a synonym of 'intervene')
'move at home' is the wordplay.
'move' becomes 'step' (step is a kind of move**).
'at home' becomes 'in' ('in' can be similar in meaning to 'at home').
'step'+'in'='STEP-IN'
'to' is the link.
(Other definitions for step in that I've seen before include "enter" , "Intervene dramatically, or at a senior level" , "Interrupt" , "Shoe with no fastenings" , "Type of garment" .)