Upset during second show is all-pervasive (11)
I believe the answer is:
omnipresent
'pervasive' is the definition.
(thesaurus)
'upset during second show' is the wordplay.
'upset' is a reversal indicator.
'during' becomes 'in' (e.g. during February means in February).
'second' becomes 'mo' (both are short periods of time).
'show' becomes 'present' (synonyms).
'in'+'mo'='inmo'
'inmo' in reverse letter order is 'omni'.
'omni'+'present'='OMNIPRESENT'
'is all' acts as a link.
I am not very happy about this link. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for omnipresent that I've seen before include "Found everywhere" , "travelling all over the place" , "Existing everywhere" , "Encountered everywhere" , "Ubiquitous" .)