The most common and most likely answer to this crossword clue is the 5 letter word TRASS
T
R
A
S
S
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The straight part
We know that "sort of cement" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case sort of cement = trass.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 TRASS mean?
TRASS noun- A white to grey volcanic tufa, formed of decomposed trachytic cinders, sometimes used as a cement.
- A coarse sort of plaster or mortar, durable in water, and used to line cisterns and other reservoirs of water.