Celebrate from Sussex to London (5)
I believe the answer is:
extol
'celebrate' is the definition.
(I've seen this before)
'from sussex to london' is the wordplay.
'from' indicates the answer is hidden within the clue.
'EXTOL' is hidden in the letters of 'sussex to london'.
(Other definitions for extol that I've seen before include "Say great things about" , "Laud; glorify" , "Magnify" , "Acclaim" , "Warmly approve of" .)