Lively dancing in ad entertains friend (8)
I believe the answer is:
animated
'lively' is the definition.
(similar in meaning)
'dancing in ad entertains friend' is the wordplay.
'dancing' indicates an anagram.
'entertains' is an insertion indicator.
'friend' becomes 'mate' (mate is a kind of friend).
'in'+'ad'='inad'
'inad' anagrammed gives 'anid'.
'anid' enclosing 'mate' is 'ANIMATED'.
(Other definitions for animated that I've seen before include "Mandate I got to be lively" , "Lively - brought to life by Disney?" , "'Lively, quick (8)'" , "Lively in diamante" , "I and mate become lively" .)