When beer starts to run over, be attentive (5)
I believe the answer is:
'attentive' is the definition.
(I've seen this in another clue)
'when beer starts to run over' is the wordplay.
'when' becomes 't' (I can't justify this - if you can you should believe this answer much more).
'beer' becomes 'ale' (type of beer).
'starts to' indicates taking the first letters.
'over' is a charade indicator (letters next to each other).
The initial letter of 'run' is 'r'.
't' after 'aler' is 'ALERT'.
'be' acts as a link.
Can you help me to learn more?
(Other definitions for alert that I've seen before include "Watchful and observant" , "In state of watchfulness" , "Signal danger" , "Watchful, sharp" , "Danger warning" .)