Cryptic crossword clue
What sounds like sweet treat, a slab making you quite full 5-1-5

The most common and most likely answer to this crossword clue is the 5 plus 1 plus 5 letter word CHOCK A BLOCK

I've seen this crossword clue in Financial Times
C
H
O
C
K
A
B
L
O
C
K

Buddy explains!

The straight part
We know that "quite full" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case quite full = chock a block.
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.

What does CHOCK A BLOCK mean?

CHOCK A BLOCK adjective
  1. (of a ship's hoisting tackle) Having the blocks drawn close together so no further movement is possible, as when the tackle is hauled to the utmost.
  2. (by extension) Jammed tightly together; very crowded; completely filled or stuffed.
CHOCK A BLOCK adverb
  1. In a crowded manner; as completely or closely as possible.

Latest crossword clues with full explanations