Shake up an inert board (7)
I believe the answer is:
entrain
'board' is the definition.
(I know that board is a is a more specific form of the action of entrain)
'shake up an inert' is the wordplay.
'shake up' indicates an anagram (I've seen 'shakes up' mean this).
'an'+'inert'='aninert'
'aninert' is an anagram of 'ENTRAIN'.
(Other definitions for entrain that I've seen before include "Put on board at the station" , "Go on board at the station" , "Get on a rail service" , "board the Orient Express?" , "Get on board railway carriages" .)