In a flap we had knocked back drink (6)
I believe the answer is:
dewlap
'in a flap' is the definition.
I can't tell whether this defines the answer.
'we had knocked back drink' is the wordplay.
'we had' becomes 'we'd' (contraction of 'we had').
'knocked back' says the letters should be written backwards.
'drink' becomes 'lap' (to lap is to drink up).
'wed' reversed gives 'dew'.
'dew'+'lap'='DEWLAP'
Can you help me to learn more?
(Other definitions for dewlap that I've seen before include "Fold of loose skin hanging from throat" , "Fold of flesh hanging below chin" , "Pendulous skin under throat" , "Fold of loose skin beneath the chin" , "Fold of skin hanging from throat of cattle" .)