Makes the mistake of pursing the lips to drink (5,2)
I believe the answer is:
slips up
'makes the mistake' is the definition.
Although both the answer and definition are verbs in their -s form, I don't understand how they can define each other.
'pursing the lips to drink' is the wordplay.
I cannot really understand how this works, but
an anagram of 'lips' is 'slip' which is present in the answer.
'drink' could be 'sup' (to sup is to drink) and 'sup' is located in the answer.
No letters remain.
This may be the basis of clue (or it may be nonsense).
'of' is the link.
Can you help me to learn more?
(Other definitions for slips up that I've seen before include "Makes a mistake" , "falls over" .)