Only lose by blundering (4)
I believe the answer is:
sole
'only' is the definition.
(I know that only can be written as sole)
'lose by blundering' is the wordplay.
'lose' can be anagrammed to 'SOLE'.
Though, I am unsure how the anagram is indicated.
Can you help me to learn more?
(Other definitions for sole that I've seen before include "One and only; part of foot" , "A lonely sort of flatfish" , "A fish; part of shoe" , "fish > that's never less than foot in length" , "European flatfish" .)