Unhappy workers finally given notice (3)
I believe the answer is:
sad
'unhappy' is the definition.
('sad' is associated in meaning with 'unhappy')
'workers finally given notice' is the wordplay.
'finally' indicates one should take the final letters.
'given' means one lot of letters go next to another.
'notice' becomes 'ad'.
The final letter of 'workers' is 's'.
's'+'ad'='SAD'
(Other definitions for sad that I've seen before include "grey" , "Miserable" , "A form of depression in winter, initially" , "Unfortunate" , "Heavy-hearted" .)