The most common and most likely answer to this crossword clue is the 18 letter word AÂ COUPLEÂ OFÂ SWELLS
I've seen this crossword clue in The Guardian
A
Â
C
O
U
P
L
E
Â
O
F
Â
S
W
E
L
L
S
Buddy explains!
The straight part
We know that "Song from Fred and Judy too" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case song from fred and judy too = a couple of swells.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.