Spot bit of orange in beer (5)
I believe the answer is:
point
'spot' is the definition.
('point' can be a synonym of 'spot')
'bit of orange in beer' is the wordplay.
'bit of' suggests taking the first letters.
'in' indicates putting letters inside.
'beer' becomes 'pint'.
The first letter of 'orange' is 'o'.
'o' going into 'pint' is 'POINT'.
(Other definitions for point that I've seen before include "The whole idea" , "Knife tip" , "Full stop; cricket position" , "Sharp end - purpose" , "Dot; fielding position" .)