Peculiarities are initially evident in very good stars (8)
I believe the answer is:
vagaries
'peculiarities' is the definition.
(vagary means a whim or peculiarity)
'are initially evident in very good stars' is the wordplay.
'initially' suggests taking the first letters.
'evident in' means one lot of letters goes inside another.
'very good' becomes 'VG' (abbreviation).
'stars' becomes 'aries' (constellation).
The initial letter of 'are' is 'a'.
'a' going within 'vg' is 'vag'.
'vag'+'aries'='VAGARIES'
(Other definitions for vagaries that I've seen before include "Unpredictable occurrences" , "Capricious acts or ideas" , "Unpredictable acts" , "Unexplained changes" , "uncertainties" .)