The most common and most likely answer to this crossword clue is the 5 plus 3 plus 5 letter word BRIDE AND GROOM
I've seen this crossword clue in The Daily Telegraph
B
R
I
D
E
A
N
D
G
R
O
O
M
Buddy explains!
The straight part
We know that "Honeymoon suite for them — grand bedroom, I suspect" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case honeymoon suite for them — grand bedroom, i suspect = bride and groom.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.