Implements action when losing streak starts (4)
I believe the answer is:
awls
'implements' is the definition.
(awl is a kind of implement)
'action when losing streak starts' is the wordplay.
'starts' says to take the initial letters.
The initial letters of 'action when losing streak' is 'AWLS'.
(Other definitions for awls that I've seen before include "Tools for punching small holes" , "Pointed hand-tools" , "Small piercing tools" , "Laws about boring tools (4)" .)