Song about drinking orange juice that's red (5)
I believe the answer is:
rioja
'red' is the definition.
(I've seen this before)
'song about drinking orange juice' is the wordplay.
'song' becomes 'air' (I've seen this before).
'about' is a reversal indicator.
'drinking' means one lot of letters goes inside another.
'orange juice' becomes 'oj'.
'air' backwards is 'ria'.
'ria' enclosing 'oj' is 'RIOJA'.
'that's' acts as a link.
(Other definitions for rioja that I've seen before include "it comes from grapevine" , "Spanish wine variety" , "Wine from northern Spain" , "Spanish drink" , "North Spanish wine" .)