Come forward, turning over tools heartlessly? (4,2)
I believe the answer is:
step up
'come forward' is the definition.
(synonyms)
'turning over tools heartlessly?' is the wordplay.
'turning over' says the letters should be written in reverse.
'tools' becomes 'puppets' ('puppet' can be a synonym of 'tool').
'heartlessly?' means to remove the middle letters (I've seen 'heartlessly' mean this).
'puppets' with its centre removed is 'pupets'.
'pupets' back-to-front is 'STEP-UP'.
(Other definitions for step up that I've seen before include "To be promoted" , "Sudden increase (in rate, output, etc)" , "Approach" , "Accelerate - promotion" , "Come forward" .)