Terrible sound drowns old mike (7)
I believe the answer is:
noisome
'terrible' is the definition.
(thesaurus)
'sound drowns old mike' is the wordplay.
'sound' becomes 'noise' (a noise is a sound).
'drowns' means one lot of letters goes inside another (I've seen this in other clues).
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'mike' becomes 'M' (phonetic alphabet: alpha, bravo, charlie etc.).
'o'+'m'='om'
'noise' placed around 'om' is 'NOISOME'.
(Other definitions for noisome that I've seen before include "Disgusting to sight or smell" , "Obnoxious" , "Disagreeable, unpleasant" , "Humming" , "Evil-smelling, objectionable (7)" .)