Earlier part in Liverpool derby (5)
I believe the answer is:
older
'earlier' is the definition.
('old' can be similar in meaning to 'early')
'part in liverpool derby' is the wordplay.
'part in' indicates a hidden word.
'OLDER' can be found hidden inside 'liverpool derby'.
(Other definitions for older that I've seen before include "More elderly" , "Less young" , "Of greater age (O, not E)" , "More aged" , "Elder" .)