Barrow runs round inside plant (6)
I believe the answer is:
carrot
'plant' is the definition.
(carrot is a kind of plant)
'barrow runs round inside' is the wordplay.
'barrow' becomes 'cart' (I can't explain this - if you can you should believe this answer much more).
'runs' becomes 'r' (cricket abbreviation).
'round' becomes 'o' (round can mean a round object).
'inside' is an insertion indicator.
'r'+'o'='ro'
'cart' enclosing 'ro' is 'CARROT'.
Can you help me to learn more?
(Other definitions for carrot that I've seen before include "Orange vegetable" , "Enticement; vegetable" , "Incentive (but not the stick)" , "One prov. used to encourage" , "The vegetable to induce" .)