Farewell to old pipe, sadly (6-3)
I believe the answer is:
toodle-pip
'farewell' is the definition.
(I know that farewell can be written as toodle-pip)
'to old pipe sadly' is the wordplay.
'sadly' indicates an anagram.
'old'+'pipe'='oldpipe'
'oldpipe' is an anagram of 'odlepip'.
'to'+'odlepip'='TOODLE-PIP'
(Other definitions for toodle-pip that I've seen before include "Take care" , "so long" , "Goodbye (dated)" , "Farewell (informal)" , "Farewell remark - dipole top (anag)" .)