Ready to see the beer doesn't get left (5)
I believe the answer is:
alert
'ready' is the definition.
(I've seen this in another clue)
'the beer doesn't get left' is the wordplay.
'the beer' becomes 'ale' (type of beer).
'doesn't get' becomes 'tr' (I can't explain this - if you can you should believe this answer much more).
'left' is a reversal indicator.
'tr' backwards is 'rt'.
'ale'+'rt'='ALERT'
'to see' acts as a link.
Can you help me to learn more?
(Other definitions for alert that I've seen before include "Watchful, sharp" , "Lively" , "'Attentive, vigilant (5)'" , "Quick to notice" , "On one's toes" .)