Endless fruit - but only one vegetable (3)
I believe the answer is:
pea
'only one vegetable' is the definition.
'pea' can be an answer for 'vegetable' (pea is a type of vegetable). I'm not certain of the 'only one' bit.
'endless fruit' is the wordplay.
'endless' means to remove the last letter.
'fruit' becomes 'pear' (pear is a kind of fruit).
'pear' with its final letter taken off is 'PEA'.
'but' is the link.
Can you help me to learn more?
(Other definitions for pea that I've seen before include "It grows in 23 Down" , "Cause of a princess's insomnia?" , "Legume" , "Climber" , "Tiny stone" .)