Move about restlessly (6)
'move about restlessly' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for fidget that I've seen before include "Wriggle" , "appear nervous" , "who can't relax" , "Make small restless movements with hands" , "Betray boredom, impatience" .)
(Other definitions for prowl that I've seen before include "Move around restlessly" , "Walk around predatorily" , "Move about with unlawful intentions" , "Walk menacingly" , "Move stealthily around" .)