Fallen wicket breaks Bradman, perhaps (4)
I believe the answer is:
down
'fallen' is the definition.
(thesaurus)
'wicket breaks bradman perhaps' is the wordplay.
'wicket' becomes 'w'.
'breaks' means one lot of letters goes inside another.
'bradman perhaps' becomes 'don' (Don Bradman).
'w' inserted inside 'don' is 'DOWN'.
(Other definitions for down that I've seen before include "Unhappy; soft feathers" , "drink at speed" , "Depressed - feathers" , "Some 13 Acrosses" , "See 10" .)