Rustic lover was upset at home (5)
I believe the answer is:
swain
'rustic lover' is the definition.
(I've seen this before)
'was upset at home' is the wordplay.
'upset' indicates anagramming the letters.
'at home' becomes 'in' ('I'm in' can mean 'I'm at home').
'was' is an anagram of 'swa'.
'swa'+'in'='SWAIN'
(Other definitions for swain that I've seen before include "Poetically, a young lover or suitor" , "fancier" , "Country boy" , "Rustic suitor" , "Male admirer" .)