Stop baseball team on the rise (4)
I believe the answer is:
stem
'stop' is the definition.
(stem can mean to stop or interrupt)
'baseball team on the rise' is the wordplay.
'baseball team' becomes 'mets' (New York Mets).
'on the rise' says the letters should be written backwards (in a down clue, letters go up).
'mets' back-to-front is 'STEM'.
(Other definitions for stem that I've seen before include "Main part of noun or verb" , "part of vegetable?" , "Stanch" , "Main stalk of a plant" , "Dam" .)