Intervene and set out to fix (4,2)
I believe the answer is:
step in
'intervene' is the definition.
(I know that intervene is a action)
'set out to fix' is the wordplay.
'out' indicates anagramming the letters (out can mean wrong or inaccurate).
'to fix' becomes 'pin' (to pin is to fix in place).
'set' is an anagram of 'ste'.
'ste'+'pin'='STEP-IN'
'and' acts as a link.
(Other definitions for step in that I've seen before include "Intervene dramatically, or at a senior level" , "Shoe with no fastenings" , "Type of garment" , "enter" , "Interrupt" .)