Get on a bit lively (6)
I believe the answer is:
obtain
'get' is the definition.
(I know that get can be written as obtain)
'on a bit lively' is the wordplay.
'lively' indicates anagramming the letters (letters get livened up or moved around).
'on'+'a'+'bit'='onabit'
'onabit' with letters rearranged gives 'OBTAIN'.
(Other definitions for obtain that I've seen before include "'Get, acquire (6)'" , "Gain possession of" , "Take possession of" , "Hold good" , "Get, procure" .)