Milk producers switched two entries in record — the woman's deceived at first (5,4)

'milk producers' is the definition.
(cows producing milk)

'record the woman's deceived at first' is the wordplay.
'record' becomes 'dairy' (I can't justify this - if you can you should believe this answer much more).
'the woman' becomes 'her' ('her' refers to a woman).
'at first' says to take the initial letters.
The first letter of 'deceived' is 'd'.
'dairy'+'her'+'d'='DAIRY HERD'

'switched two entries in' is the link.
This may not be right. Some or all of it may belong to another bit of the clue.