No great shakes on the Richter scale (6)
I believe the answer is:
tremor
'no great shakes' is the definition.
'tremor' can be an answer for 'shakes' (thesaurus). I am not certain of the 'no great' bit.
'on the richter scale' is the wordplay.
I cannot really understand how this works, but
'on' could be 're' ('on' can be mean 'with reference to') and 're' is located in the answer.
'the' could be 't' (the is pronounced as a 't' sound in some dialects) and 't' is found within the answer.
The remaining letters 'mor' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for tremor that I've seen before include "Small earthquake" , "Small shock" , "feeling of excitement" , "A little agitation" , "Small vibration" .)