Eton was upset? It's not a problem! (2,5)
I believe the answer is:
no sweat
'not a problem' is the definition.
'eton was upset?' is the wordplay.
'upset?' is an anagram indicator (I've seen 'upset' mean this).
'eton'+'was'='etonwas'
'etonwas' is an anagram of 'NO SWEAT'.
'it's' is the link.
(Other definitions for no sweat that I've seen before include "OK" , "Not a problem (US colloq.)" , "It's not a problem (result of using antiperspirant?)" , "That's not a problem!" , "fine" .)