Dissatisfaction of tiddly nun that is returning drinks (5)
I believe the answer is:
ennui
'dissatisfaction' is the definition.
(ennui is a kind of dissatisfaction)
'tiddly nun that is returning drinks' is the wordplay.
'tiddly' indicates anagramming the letters.
'that is' becomes 'ie' (short for Latin 'id est', 'that is').
'returning' shows that the letters should be reversed in order.
'drinks' indicates putting letters inside (inserted letters are consumed or drunk).
'ie' written backwards gives 'ei'.
'nun' is an anagram of 'nnu'.
'nnu' inserted within 'ei' is 'ENNUI'.
'of' acts as a link.
(Other definitions for ennui that I've seen before include "Low interest rate" , "Effect of boredom" , "to make one list less when connected" , "Listless feeling" , "doldrums" .)