Imitate rock, music genre served up (6)
I believe the answer is:
parrot
'imitate' is the definition.
(I've seen this in another clue)
'rock music genre served up' is the wordplay.
'rock' becomes 'tor' (a tor is a rocky peak).
'music genre' becomes 'rap' (I've seen this in another clue).
'served up' says the letters should be written in reverse (in a down clue, going upwards).
'tor'+'rap'='torrap'
'torrap' back-to-front is 'PARROT'.
(Other definitions for parrot that I've seen before include "Squawking bird" , "Eg, macaw" , "18's [BIRD]" , "Tropical bird for Pat Orr" , "Vividly coloured bird" .)