Baseman's blunder (5)
I believe the answer is:
error
'baseman's blunder' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for error that I've seen before include "Faulty judgment" , "Fallacy, mistake" , "Solecism" , "Slip, mistake" , "A mistake or inaccuracy" .)