Weak, unconvincing (4)
I believe the answer is:
lame
<span class="explanation-format__ClueExplanation">This clue is a double definition.<br/ ><br/ >'<span class="explanation-format__original">weak</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(similar in meaning)</span><br/ ><br/ >'<span class="explanation-format__original">unconvincing</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ ></span>
(Other definitions for lame that I've seen before include "Disabled in the feet or legs" , "Having impaired walking ability" , "Halt" , "Unable to walk without difficulty" , "Disabled in leg or foot" .)