Only to lose badly (4)
I believe the answer is:
sole
'only' is the definition.
(synonyms)
'lose badly' is the wordplay.
'badly' indicates anagramming the letters.
'lose' with letters rearranged gives 'SOLE'.
'to' acts as a link.
(Other definitions for sole that I've seen before include "Unique" , "Flatfish; exclusive" , "piece of leather" , "fish in the sea!" , "Shoe part -- lone" .)