Unfit, fat Don out running from one place to another (2,3,3)
I believe the answer is:
to and fro
'from one place to another' is the definition.
(synonyms)
'unfit fat don out running' is the wordplay.
'unfit' indicates anagramming the letters.
'out running' becomes 'ro' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'fat'+'don'='fatdon'
'fatdon' anagrammed gives 'toandf'.
'toandf'+'ro'='TO-AND-FRO'
Can you help me to learn more?
(Other definitions for to and fro that I've seen before include "Directions of oscillation" , "This way and that, back and forth" , "Backwards and forwards" , "From place to place" , "Back and forth like pendulum (2.3.3)" .)