Thus it is seen in Oliver Goldsmith (4)
I believe the answer is:
ergo
'thus' is the definition.
(I've seen this in another clue)
'seen in oliver goldsmith' is the wordplay.
'seen in' says the answer is hidden in the clue.
'ERGO' is hidden within 'oliver goldsmith'.
'it is' is the link.
(Other definitions for ergo that I've seen before include "'Therefore, to the old Romans (4)'" , "so philosopher wrote in Latin" , "as a consequence" , "Consequently" , "'Cogito, ---- sum'" .)