Light beer after a drop of pilsner (4)
I believe the answer is:
pale
'light' is the definition.
(similar in meaning)
'beer after a drop of pilsner' is the wordplay.
'beer' becomes 'ale' (type of beer).
'after' says to put letters next to each other.
'a drop of' indicates taking the first letters.
The initial letter of 'pilsner' is 'p'.
'ale' put after 'p' is 'PALE'.
(Other definitions for pale that I've seen before include "Light-coloured" , "It's unacceptable to go beyond this" , "Containing little colour" , "Light in colour" , "A bit of fencing" .)