The most common and most likely answer to this crossword clue is the 5 letter word DENSE
D
E
N
S
E
More clues leading to the result DENSE
- Thick section in garden seat
- Slow to understand Democrat, unable to relax, blowing top
- Girl one leaves is thick
- Old penny dreadful seen as impenetrable
- Thick studies finally complete
- Not very bright, but studies English
- Studies English? Foolish
- Impenetrable studies before end of course
- Not very bright, needs to be properly organised
- Impenetrable Oriental studies have precedence
Buddy explains!

The straight part
We know that "Slow to understand" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case slow to understand = dense.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 DENSE mean?
DENSE noun- A thicket.
- Having relatively high density.
- Compact; crowded together.
- Thick; difficult to penetrate.
- Opaque; allowing little light to pass through.
- Obscure, or difficult to understand.
- Being a subset of a topological space that approximates the space well. See Wikipedia article on dense sets for mathematical definition.
- (of a person) Slow to comprehend; of low intelligence.