Qualifications of reactionary Rees-Mogg’s faction set in stone (7)
I believe the answer is:
degrees
'qualifications' is the definition.
(I have seen 'Educational qualifications ' mean 'degrees' so perhaps 'qualifications' could also mean 'degrees')
'reactionary rees-mogg's faction set in stone' is the wordplay.
'reactionary' says the letters should be written in reverse (reactions happen in the opposite direction).
'rees-mogg's faction' becomes 'erg' (European Research Group includes Jacob Rees-Mogg).
'set in' means one lot of letters goes inside another.
'stone' becomes 'seed' (eg the stone from a fruit).
'erg' going into 'seed' is 'seerged'.
'seerged' in reverse letter order is 'DEGREES'.
'of' is the link.
(Other definitions for degrees that I've seen before include "Revolutionary measures" , "Measures for arcs and angles" , "distinctions that are academic" , "Measure for arcs and angles" , "Educational qualifications" .)