Spy pens farewell, initially navigating in a new direction (2,1,7)
I believe the answer is:
at a tangent
'in a new direction' is the definition.
(as in going off at a tangent)
'spy pens farewell initially navigating' is the wordplay.
'spy' becomes 'agent' (secret agent).
'pens' indicates putting letters inside (to pen can mean to contain or imprison).
'farewell' becomes 'ta ta' (I've seen this in another clue).
'initially' indicates taking the first letters.
The first letter of 'navigating' is 'n'.
'tata'+'n'='tatan'
'agent' placed around 'tatan' is 'AT A TANGENT'.
(Another definition for at a tangent that I've seen is " In a divergent train of thought or action".)