Dance round on one leg, say (5)
I believe the answer is:
limbo
'dance' is the definition.
(I've seen this before)
'round on one leg say' is the wordplay.
'round' becomes 'o' (round can mean a round object).
'on' means one lot of letters go next to another.
'one leg say' becomes 'limb' (leg is a kind of limb).
'o' put after 'limb' is 'LIMBO'.
(Other definitions for limbo that I've seen before include "Once supposed abode of the souls of unbaptized infants" , "Dance - place of oblivion" , "Waiting state; Caribbean dance" , "Where waiters are" , "Intermediate state; obscurity" .)