Paid athlete (3)
I believe the answer is:
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">paid athlete</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for pro that I've seen before include "In favour of; advantage" , "With qualifications" , "Paid worker" , "Of argument, say, in favour of" , "In brief, he's no amateur" .)