Minor earthquake set capital right back (6)
I believe the answer is:
tremor
'minor earthquake' is the definition.
(I've seen this before)
'set capital right back' is the wordplay.
'set capital' becomes 'rome' (capital of Italy. I am not sure about the 'set' bit.).
'right' becomes 'rt' (abbreviation as in Rt Hon- the Right Honourable).
'back' is a reversal indicator.
'rome'+'rt'='romert'
'romert' back-to-front is 'TREMOR'.
Can you help me to learn more?
(Other definitions for tremor that I've seen before include "Vibration - shaking" , "Quaver" , "A slight shake, body or earth" , "feeling of excitement" , "make one shake" .)