Struggle with drink, its source concealing painful extremes (7)
I believe the answer is:
grapple
'struggle with' is the definition.
(I've seen this before)
'drink its source concealing painful extremes' is the wordplay.
'drink its source' becomes 'grape' (wine is made from grapes).
'concealing' means one lot of letters goes inside another.
'extremes' says to hollow out the word (remove centre letters).
'painful' with its middle taken out is 'pl'.
'grape' placed around 'pl' is 'GRAPPLE'.
(Other definitions for grapple that I've seen before include "struggle" , "Lay hold of" , "Go to work on" , "Engage in a close fight" , "Wrestle mentally (with)" .)