Flashy old wreck going round the youth centre (4)
I believe the answer is:
loud
'flashy' is the definition.
(I know that flashy can be written as loud)
'old wreck going round the youth centre' is the wordplay.
'wreck' is an anagram indicator.
'going round' is an insertion indicator (some letters go around others).
'the youth centre' becomes 'u' (middle letter of the word 'youth').
'old' anagrammed gives 'lod'.
'lod' placed around 'u' is 'LOUD'.
(Other definitions for loud that I've seen before include "strongly audible" , "Resounding" , "This speaker is" , "Forte" , "Deafening" .)