Start working in exchange with old name (6,2)
I believe the answer is:
switch on
'start working' is the definition.
(to switch something on is to start it working)
'exchange with old name' is the wordplay.
'exchange' becomes 'switch' (synonyms).
'with' says to put letters next to each other.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'name' becomes 'n' (common abbreviation e.g. on forms).
'switch'+'o'+'n'='SWITCH ON'
'in' acts as a link.
(Other definitions for switch on that I've seen before include "Operate" , "start" , "fire" , "Activate (equipment)" , "Engage an electrical device" .)