The most common and most likely answer to this crossword clue is the 4 letter word HALF
I've seen this crossword clue in The Times
H
A
L
F
More clues leading to the result HALF
- Trouble-making sextet?
- Relative in MI6?
- Female joining women's group in station is an idiot
- 50% of all sheds last fine with hard roofing
- Finally crash via fall of fifty per cent
- 50% healthy, not completely fine at first
- Female attached to Henry — one of six better ones for him?
- Henry with head for figures gets one over a couple
- Rugby player hits low note, roughly a fortnightly occurrence
- Stole — away but not all the way?
Buddy explains!

The straight part
We know that "roughly a fortnightly occurrence" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case roughly a fortnightly occurrence = half.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 HALF mean?
HALF noun- One of two usually roughly equal parts into which anything may be divided, or considered as divided.
- Half of a standard measure; frequently used for half a pint of beer or cider.
- (preceded by “a” or a number) The fraction obtained by dividing 1 by 2.
- Part; side; behalf.
- Any of the three terms at Eton College, for Michaelmas, Lent, and summer.
- A half sibling.
- A child ticket.
- To halve.
- Consisting of a half (1/2, 50%).
- Consisting of some indefinite portion resembling a half; approximately a half, whether more or less; partial; imperfect.
- (of a sibling) Having one parent (rather than two) in common.
- (rare, of a relative other than a sibling) Related through one common grandparent or ancestor rather than two.
- In two equal parts or to an equal degree.
- In some part approximating a half.
- Partially; imperfectly.
- A half-hour after, thirty minutes after (used with the number of the hour).