Protest turned around by union that's already there (2,4)
I believe the answer is:
in situ
'already there' is the definition.
(situated in the original place)
'protest turned around by union' is the wordplay.
I cannot quite see how this works, but
'union' could be 'tu' (short for trade union) and 'tu' is found in the answer.
This explanation may well be incorrect...
'that's' acts as a link.
Can you help me to learn more?
(Other definitions for in situ that I've seen before include "Being in the original position, not having been moved" , "Latin meaning 'on site'" , "Occupying the right position" , "In its original place, in Latin" , "at original location" .)