Frustrated being of idle disposition (6)
I believe the answer is:
foiled
'frustrated' is the definition.
(I know that frustrated can be written as foiled)
'of idle disposition' is the wordplay.
'disposition' is an anagram indicator.
'of'+'idle'='ofidle'
'ofidle' is an anagram of 'FOILED'.
'being' is the link.
(Other definitions for foiled that I've seen before include "Thwarted, frustrated" , "Thwarted with sword?" , "Thwarted, defeated" , "Prevented the success of" .)