Wiggling a leg gets one supple (5)
I believe the answer is:
agile
'supple' is the definition.
(I've seen this in another clue)
'wiggling a leg gets one' is the wordplay.
'wiggling' indicates anagramming the letters (letters wiggle around).
'gets' means one lot of letters goes inside another (gets can mean captures or absorbs).
'one' becomes 'i' (Roman numeral).
'a'+'leg'='aleg'
'aleg' with letters rearranged gives 'agle'.
'agle' enclosing 'i' is 'AGILE'.
(Other definitions for agile that I've seen before include "Quick-moving, supple" , "Physically quick and nimble" , "Moving quickly/easily" , "Nimble, active" , "Lithely moving" .)