Like a loud blonde's relationship? (4,6)
I believe the answer is:
love affair
'relationship?' is the definition.
(love affair is a kind of relationship)
'like a loud blonde's' is the wordplay.
'like' becomes 'love' (loving is a kind of liking**).
'loud' becomes 'f' (A musical term).
'blonde' becomes 'fair' ('fair' can be similar in meaning to 'blonde').
'love'+'a'+'f'+'fair'='LOVE-AFFAIR'
(Other definitions for love affair that I've seen before include "A (short?) romantic relationship" , "Romance" .)