Return Yankee, libelled now and then (5)
I believe the answer is:
yield
'return' is the definition.
(I know that return can be written as yield)
'yankee libelled now and then' is the wordplay.
'yankee' becomes 'Y' (phonetic alphabet: alpha, bravo, charlie etc.).
'now and then' means one should take alternating letters (letters taken on a regular basis, now and then).
The alternating letters of 'libelled' are 'ield'.
'y'+'ield'='YIELD'
(Other definitions for yield that I've seen before include "Bring forth" , "Investment interest" , "Cede, give way" , "Surrenders or bears as a crop" , "size of crop" .)