Snake reached ground, circling round very quietly (10)
I believe the answer is:
copperhead
'snake' is the definition.
(copperhead is a kind of snake)
'reached ground circling round very quietly' is the wordplay.
'ground' indicates an anagram ('grind' the letters into a new form).
'circling' indicates putting letters inside (circling can mean going around or containing).
'round' becomes 'o' (round can mean a round object).
'very quietly' becomes 'pp' (musical abbreviation for pianissimo).
'reached' with letters rearranged gives 'cerhead'.
'o'+'pp'='opp'
'cerhead' placed around 'opp' is 'COPPERHEAD'.
(Other definitions for copperhead that I've seen before include "Venomous type" , "Venomous, reddish-brown American snake" , "Reptile" , "venomous sort" , "Policeman brains snake" .)