Son given very warm drink (4)
I believe the answer is:
shot
'drink' is the definition.
(I've seen this before)
'son given very warm' is the wordplay.
'son' becomes 's'.
'given' says to put letters next to each other.
'very warm' becomes 'hot' (I've seen this before).
's'+'hot'='SHOT'
(Other definitions for shot that I've seen before include "Fired or filmed" , "Firing of a gun" , "Sound of gun" , "Small drink of spirits" , "Small drink of liquor" .)