Tropical plant better thus? Let me think (8)
I believe the answer is:
capsicum
'tropical plant' is the definition.
(capsicum is a type of tropical plant)
'better thus? let me think' is the wordplay.
'better' becomes 'cap' (both can mean to beat somebody else's attempt).
'thus?' becomes 'sic' ('thus' in Latin).
'let me think' becomes 'um' (expression of hesitation).
'cap'+'sic'+'um'='CAPSICUM'
(Other definitions for capsicum that I've seen before include "vegetable?" , "seeds" , "Pepper supplier" , "Pepper fruit" , "American pepper" .)