Loud user of tongue in a flash (7)
I believe the answer is:
flicker
'a flash' is the definition.
(flicker is a kind of flash)
'loud user of tongue in' is the wordplay.
'loud' becomes 'f' (short for forte - 'loud' in music).
'user of' becomes 'er' (I can't justify this - if you can you should believe this answer much more).
'tongue' becomes 'lick'.
'in' indicates putting letters inside.
'f'+'er'='fer'
'fer' enclosing 'lick' is 'FLICKER'.
Can you help me to learn more?
(Other definitions for flicker that I've seen before include "Shine unsteadily; waver" , "Twinkle" , "Spark" , "Woodpecker" , "Burn or shine unsteadily" .)