A strong impulse (4)
I believe the answer is:
urge
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">a strong impulse</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for urge that I've seen before include "Capital of Colombia" , "Impel, egg on" , "Appeal to" , "Egg on, encourage to proceed" , "Sudden inclination to do something" .)