In the centre, more of a shake (6)
I believe the answer is:
tremor
'a shake' is the definition.
(I know that tremor is a type of shake)
'in the centre more of' is the wordplay.
'in' indicates the answer is hidden within the clue.
'TREMOR' can be found hidden inside 'centre more of'.
(Other definitions for tremor that I've seen before include "Vibration - shaking" , "Involuntary quiver" , "Small earthquake" , "A slight shake, perhaps of earth" , "Nervousness" .)