Pipers playing before queen start to exude sweat (8)
I believe the answer is:
perspire
'sweat' is the definition.
(I know that sweat can be written as perspire)
'pipers playing before queen start to exude' is the wordplay.
'playing' indicates an anagram.
'before' means one lot of letters go next to another.
'queen' becomes 'r' (abbreviation for regina, e.g. in ER ).
'start to' says to take the initial letters.
The first letter of 'exude' is 'e'.
'pipers' with letters rearranged gives 'perspi'.
'perspi'+'r'+'e'='PERSPIRE'
(Other definitions for perspire that I've seen before include "Sweat (as a lady does?)" , "Sweat politely" , "Swelter" , "for every shoot" , "Exude" .)