Being of one mind to ignore adult vice (5)
I believe the answer is:
greed
'vice' is the definition.
(I've seen this before)
'being of one mind to ignore adult' is the wordplay.
'being of one mind' becomes 'agreed' (I've seen this before).
'to ignore' indicates named letters should be taken away.
'adult' becomes 'a' (abbreviation).
'agreed' with 'a' taken out is 'GREED'.
(Other definitions for greed that I've seen before include "Vice" , "Eager desire" , "Wanting too much" , "Rapacious desire" , "Rapacity" .)