Trumped in error that's indiscreet (9)
I believe the answer is:
imprudent
'indiscreet' is the definition.
(similar in meaning)
'trumped in error' is the wordplay.
'error' indicates anagramming the letters.
'trumped'+'in'='trumpedin'
'trumpedin' with letters rearranged gives 'IMPRUDENT'.
'that's' is the link.
(Other definitions for imprudent that I've seen before include "not wise" , "Reckless" , "Without forethought" , "Unwise" , "Rash, lacking discretion" .)