The most common and most likely answer to this crossword clue is the 5 letter word SEVEN
I've seen this crossword clue in The Times
S
E
V
E
N
More clues leading to the result SEVEN
- Six minus nine’s still a positive integer
- Sons just like fish — and try game
- All dwarfs, small and equal
- Number second, like two!
- Small flat playing card?
- Noticed collecting first character of vehicle number
- Number of sins still to be overcome by Saint
- Oddly cheery native’s tendency towards infidelity
- First lady wears clothes of satin — they were magnificent in the film
- Poles embracing woman in prime
Buddy explains!

The straight part
We know that "tendency towards infidelity" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case tendency towards infidelity = seven.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 SEVEN mean?
SEVEN noun- The digit/figure 7 or an occurrence thereof.
- A card bearing seven pips.
- A numerical value equal to 7; the number following six and preceding eight. This many dots: (•••••••).
- Describing a group or set with seven elements.