Thick digit (5)
I believe the answer is:
thumb
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">thick digit</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 thumb that I've seen before include "Hitchhike - ..... a lift" , "Try to get free ride" , "Tom ___ , traditional hero of English folklore" , "Hand digit" , "Opposable digit" .)