Party dismisses Unionist leader, a number of overseas politicians and those employing scientists (12)
I believe the answer is:
laboratories
'scientists' is the definition.
Although both the answer and definition are plural nouns, I don't see how they can define each other.
'party dismisses unionist leader a number of overseas politicians and those' is the wordplay.
I cannot really understand how this works, but
'party' could be 'labor' (Labor Party, Australian political party) and 'labor' is found in the answer.
'leader' could be 'e' (I've seen this in other clues) and 'e' is located in the answer.
'a' is within the answer.
'number' could be 'i' (I is an example) and 'i' is found in the answer.
'of' could be 'o' and 'o' is located in the answer.
This may be the basis of the clue (or it may be nonsense).
'employing' acts as a link.
Can you help me to learn more?
(Another definition for laboratories that I've seen is " Rooms for scientists".)