Develops odds on heavy defeats (7)
I believe the answer is:
sprouts
'develops' is the definition.
(sprouting is a kind of developing)
'odds on heavy defeats' is the wordplay.
'odds' becomes 'sp' (betting abbreviation for starting price).
'on' says to put letters next to each other.
'heavy defeats' becomes 'routs' (rout is a kind of defeat. I am not sure about the 'heavy' bit.).
'sp'+'routs'='SPROUTS'
Can you help me to learn more?
(Other definitions for sprouts that I've seen before include "Green vegetable" , "Small cabbage-like veg." , "Green vegetables" , "[TRIMMING]" , "Grows vegetables" .)