Ready to drink a bit of porter (5)
I believe the answer is:
alert
'ready' is the definition.
(I've seen this in another clue)
'drink a bit of porter' is the wordplay.
'drink' becomes 'ale' (type of beer).
'a bit of porter' becomes 'rt' (I can't explain this - if you can you should give a lot more credence to this answer).
'ale'+'rt'='ALERT'
'to' acts as a link.
Can you help me to learn more?
(Other definitions for alert that I've seen before include "'Attentive, vigilant (5)'" , "Watchful; warning" , "On the ball" , "Wakeful, observant" , "Thinking and acting quickly" .)