Conduct was largely good at start of evening (4)
I believe the answer is:
wage
'conduct' is the definition.
(both can mean to carry out)
'was largely good at start of evening' is the wordplay.
'largely' means to remove the last letter.
'good' becomes 'g' (abbreviation).
'at start of' indicates taking the first letters.
The first letter of 'evening' is 'e'.
'was' with its final letter removed is 'wa'.
'wa'+'g'+'e'='WAGE'
(Other definitions for wage that I've seen before include "Salary" , "Payment to an employee" , "Engage in - pay" , "Amount earned" , "Regular payment for work" .)