Socialist to change measure during recession (3,5)
I believe the answer is:
red shift
'measure during recession' is the definition.
(phenomenon occurring when measuring receding waves)
'socialist to change' is the wordplay.
'socialist' becomes 'red' (red is a kind of socialist).
'to change' becomes 'shift' ('shift' can be a synonym of 'change').
'red'+'shift'='RED SHIFT'
(Other definitions for red shift that I've seen before include "Receding-starlight phenomenon" , "Wavelength change of fast-moving objects" , "Aspect of spectrum" , "evidence of recession?" .)