Understand lies are wrong (7)
I believe the answer is:
realise
'understand' is the definition.
('understand'->'realize' is in my internal thesaurus and 'ize'->'ise')
'lies are wrong' is the wordplay.
'wrong' indicates an anagram.
'lies'+'are'='liesare'
'liesare' anagrammed gives 'REALISE'.
(Other definitions for realise that I've seen before include "Achieve, make" , "get cash for property" , "Twig" , "Ears lie (anag.)" , "Discover" .)