March perhaps failing to start, say - none getting active (2,3,2)
'active' is the definition.
'march perhaps failing to start say none' is the wordplay.
'march perhaps' becomes 'month' (march is a kind of month).
'failing to start' means to remove the first letter.
'say' becomes 'eg'.
'none' becomes 'o'.
'month' with its initial letter taken off is 'onth'.
'onth'+'eg'+'o'='ON THE GO'
'getting' acts as a link.
(Other definitions for on the go that I've seen before include "Keeping busy, not stopping", "Very active (colloq.)", "Very busy, in constant motion", "Active, in constant motion", "Active and energetic".)