Large drink bottles fail to balance (4)
I believe the answer is:
slip
'fail to balance' is the definition.
I can't judge whether this definition defines the answer.
'large drink bottles' is the wordplay.
'large' becomes 'L' (eg in clothes sizes).
'drink' becomes 'sip' (sipping is a kind of drinking).
'bottles' is an insertion indicator (bottle can mean to contain).
'l' put inside 'sip' is 'SLIP'.
Can you help me to learn more?
(Other definitions for slip that I've seen before include "Slight error" , "Loose one's footing" , "Glide; petticoat" , "Sole lapse" , "Lose footing or make mistake" .)