Carefully observe indefinite number returning to Lincoln, Nebraska (4,4)
I believe the answer is:
nota bene
'carefully observe' is the definition.
(Italian for 'note well', as in N.B. before a note)
'indefinite number returning to lincoln nebraska' is the wordplay.
'indefinite number' becomes 'n' (I've seen this in other clues).
'returning' says the letters should be written in reverse.
'lincoln' becomes 'abe'.
'nebraska' becomes 'ne'.
'to' backwards is 'ot'.
'n'+'ot'+'abe'+'ne'='NOTA BENE'
(Other definitions for nota bene that I've seen before include "NB in full" , "Expansion of Latin notation N.B." , "'Mark well, in Latin (4,4)'" , "Look carefully" , "Observe carefully (Latin)" .)