It's different in Rotherhithe (5)
I believe the answer is:
other
'it's different' is the definition.
(similar in meaning)
'in rotherhithe' is the wordplay.
'in' indicates the answer is hidden within the clue.
'OTHER' can be found hidden inside 'rotherhithe'.
(Other definitions for other that I've seen before include "Different; alternate" , "Throe (anag)" , "Alternative - unrelated" , "Different, alternative" , "Second" .)