Loud Welshwoman entertains singer keeping time (10)
I believe the answer is:
stentorian
'loud' is the definition.
('stentorian' can be similar in meaning to 'loud')
'welshwoman entertains singer keeping time' is the wordplay.
'welshwoman' becomes 'sian' (common Welsh name).
'entertains' is an insertion indicator.
'singer' becomes 'tenor' (tenor is a kind of singer**).
'keeping' means one lot of letters goes inside another.
'time' becomes 't'.
'tenor' placed around 't' is 'tentor'.
'sian' going around 'tentor' is 'STENTORIAN'.
(Other definitions for stentorian that I've seen before include "Strident" , "(Of a person's voice) loud and powerful" , "booming" .)