Cruel and senseless endlessly suppressing buzz (7)
I believe the answer is:
inhuman
'cruel' is the definition.
(I've seen this before)
'senseless endlessly suppressing buzz' is the wordplay.
'senseless' becomes 'inane' (I've seen this before).
'endlessly' means to remove the last letter.
'suppressing' indicates putting letters inside.
'buzz' becomes 'hum' ('hum' can be a synonym of 'buzz').
'inane' with its last letter taken away is 'inan'.
'inan' going around 'hum' is 'INHUMAN'.
'and' acts as a link.
(Other definitions for inhuman that I've seen before include "diabolical ..." , "Cruel, barbaric" , "Without compunction" , "barbarous and brutal" , "Cruel, bestial" .)