Shot in the arm (6)
I believe the answer is:
fillip
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">shot in the arm</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for fillip that I've seen before include "As tonic" , "Incitement" , "Get a boost" , "Stimulus or incentive" , "Encouragement, stimulus" .)