Warned I've dad's pants (7)
I believe the answer is:
advised
'warned' is the definition.
(I've seen this before)
'i've dad's pants' is the wordplay.
'pants' indicates an anagram (UK informal term for 'nonsense' or 'rubbish').
'ive'+'dads'='ivedads'
'ivedads' is an anagram of 'ADVISED'.
(Other definitions for advised that I've seen before include "Gave guidance to" , "Sensible; recommended (a course of action)" , "Notified" , "Informed" , "Counselled" .)