Little boys' lies about a terrible dad (7)
I believe the answer is:
laddies
'little boys'' is the definition.
(laddie can informally mean a boy)
'lies about a terrible dad' is the wordplay.
'about' means one lot of letters goes inside another.
'a terrible' indicates an anagram.
'dad' is an anagram of 'add'.
'lies' placed around 'add' is 'LADDIES'.
(Other definitions for laddies that I've seen before include "Boys" , "young men" .)