Strikes hit workers initially involved in courses (7)

'courses' is the definition.
The definition and answer can be both acts as well as being plural nouns.
Maybe you can see an association between them that I don't see?

'strikes hit workers initially involved' is the wordplay.
'strikes hit' becomes 'thacks' (I am not sure about this - if you are sure you should believe this answer much more).
'initially' says to take the initial letters.
'involved' indicates putting letters inside.
The initial letter of 'workers' is 'w'.
'thacks' going around 'w' is 'THWACKS'.

'in' acts as a link.

Can you help me to learn more?