Pea, bean or lentil (5)
I believe the answer is:
pulse
<span class="explanation-format__ClueExplanation">This clue is a double definition.<br/ ><br/ >'<span class="explanation-format__original">pea</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(thesaurus)</span><br/ ><br/ >'<span class="explanation-format__original">bean or lentil</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(I know that bean is a type of pulse)</span><br/ ><br/ ></span>
(Other definitions for pulse that I've seen before include "A vital sign turning" , "It beats - peas and beans" , "Musical beat; edible seeds" , "Rhythmic beat" , "lentils etc" .)