Fickle Methuselah no longer has the hots for mimics (8)
I believe the answer is:
emulates
'mimics' is the definition.
(emulate can mean to mimic or imitate)
'fickle methuselah no longer has the hots' is the wordplay.
'fickle' indicates anagramming the letters.
'no longer has' is a deletion indicator.
'the hots' becomes 'hh' (two H's - H means Hot eg on taps).
'methuselah' with 'hh' taken out is 'metusela'.
'metusela' is an anagram of 'EMULATES'.
'for' is the link.
(Other definitions for emulates that I've seen before include "Tries hard to be equal to" , "tries to follow" , "Copies" , "Imitates" .)