Light pressure used with beer (4)
I believe the answer is:
pale
'light' is the definition.
(similar in meaning)
'pressure used with beer' is the wordplay.
'pressure' becomes 'p' (abbreviation).
'used with' says to put letters next to each other.
'beer' becomes 'ale' (type of beer).
'p'+'ale'='PALE'
(Other definitions for pale that I've seen before include "wooden post" , "Colourless" , "picket" , "A bit of fencing" , "Not bright - limit" .)