Exudation from leguminous plants? (3)
I believe the answer is:
gum
'exudation' is the definition.
(I know that gum is a type of exudation)
'from leguminous plants?' is the wordplay.
'from' indicates a hidden word.
'GUM' is hidden within 'leguminous plants'.
(Other definitions for gum that I've seen before include "Sticky substance and mouth tissue" , "Sticky stuff - tree" , "Adhesive for chewing" , "surrounding roots of teeth?" , "Chewed sweet" .)