Lively beer Roosevelt drained (5)
I believe the answer is:
alert
'lively' is the definition.
(I know that lively can be written as alert)
'beer roosevelt drained' is the wordplay.
'beer' becomes 'ale' (type of beer).
'drained' suggests removing the centre.
'roosevelt' with its middle taken out is 'rt'.
'ale'+'rt'='ALERT'
(Other definitions for alert that I've seen before include "Watchfully awake" , "Wide-awake and watchful" , "Warning signal" , "Awake, attentive" , "Wide awake and watchful" .)