Farm labourer, lacking company, upset over a sports event (7)
I believe the answer is:
regatta
'sports event' is the definition.
(I've seen this before)
'farm labourer lacking company upset over a' is the wordplay.
'farm labourer' becomes 'cottager'.
'lacking' indicates named letters should be taken away.
'company' becomes 'co' (abbreviation).
'upset' says the letters should be written backwards.
'over' means one lot of letters go next to another.
'cottager' with 'co' taken away is 'ttager'.
'ttager' back-to-front is 'regatt'.
'regatt'+'a'='REGATTA'
(Other definitions for regatta that I've seen before include "It could involve a lot of rowing" , "race on the river" , "Yacht-racing event" , "Racing boats" , "Race meeting for boats" .)