Become somewhat fidgety (3)
I believe the answer is:
get
'become' is the definition.
(I know that become can be written as get)
'somewhat fidgety' is the wordplay.
'somewhat' indicates a hidden word.
'GET' can be found hidden inside 'fidgety'.
(Other definitions for get that I've seen before include "Understand" , "Procure or secure" , "Acquire" , "Fetch or obtain" , "Procure from vegetables" .)