Savage bits of detail are flagged up (5)
I believe the answer is:
feral
'savage' is the definition.
(synonyms)
'bits of detail are flagged up' is the wordplay.
'bits of' indicates the answer is hidden within the clue.
'up' says the letters should be written in reverse (in down clue: letters go upwards).
'laref' is hidden in the letters of 'detail are flagged'.
'laref' reversed gives 'FERAL'.
(Other definitions for feral that I've seen before include "Of plants or animals, wild" , "Wild (though once tame)" , "'Savage, wild (5)'" , "Escaped-into-wild (animal)" , "Wild and menacing" .)