Leaves American university so upset about it (5)
I believe the answer is:
omits
'leaves american' is the definition.
The definition and answer can be both related to thinking as well as being verbs in their -s form.
Maybe they are linked in a way I don't understand?
'university so upset about it' is the wordplay.
'university' becomes 'mit' (I've seen this in other clues).
'upset' indicates an anagram.
'about it' means one lot of letters goes inside another.
'so' anagrammed gives 'os'.
'mit' placed into 'os' is 'OMITS'.
Can you help me to learn more?
(Other definitions for omits that I've seen before include "Forgets" , "skips" , "Leaves out or neglects" , "overlooks" , "misses out" .)