Piercing Spartacus firstly with spear (8)
I believe the answer is:
strident
'piercing' is the definition.
(thesaurus)
'spartacus firstly with spear' is the wordplay.
'spartacus firstly' becomes 's' (I can't justify this - if you can you should give a lot more credence to this answer).
'with' means one lot of letters go next to another.
'spear' becomes 'trident' (trident is a kind of spear).
's'+'trident'='STRIDENT'
Can you help me to learn more?
(Other definitions for strident that I've seen before include "Harsh, grating" , "making a lot of noise" , "harsh sound" , "Tumultuous" , "Unpleasantly rough" .)