Amiable, and at close of day extremely lively (8)
I believe the answer is:
friendly
'amiable' is the definition.
(similar in meaning)
'at close of day extremely lively' is the wordplay.
'at' says to put letters next to each other.
'close of day' becomes 'Fri end' (the end of Friday).
'extremely' suggests removing the centre.
'lively' with its centre taken out is 'ly'.
'friend' put next to 'ly' is 'FRIENDLY'.
'and' is the link.
(Other definitions for friendly that I've seen before include "Amiable" , "Sociable" , "Affable" , "One is obviously on good terms with" , "such a society" .)