Knock back beer, any amount, in style (4)
I believe the answer is:
elan
'style' is the definition.
(I know that style can be written as elan)
'knock back beer any amount' is the wordplay.
'knock back' says the letters should be written in reverse.
'beer' becomes 'ale' (type of beer).
'any amount' becomes 'n' (N is an example. I am not sure about the 'any' bit.).
'ale' back-to-front is 'ela'.
'ela'+'n'='ELAN'
'in' acts as a link.
Can you help me to learn more?
(Other definitions for elan that I've seen before include "French dish in lane" , "fizz" , "French flair" , "Verve and dash" , "Stylish elegance" .)