The most common and most likely answer to this crossword clue is the 4 letter word BECK
I've seen this crossword clue in The Times
B
E
C
K
More clues leading to the result BECK
- Gesture to attract attention of runner in the countryside
- Sign to approach / stream
- Stream reversed, as announced at Balmoral?
- Live fashion logo gets the nod
- Give the nod to Miss Sharp, Thackeray’s ultimate failure
- Sign for Northern stream
- Make out with boy replacing lead musician
- Call with little flower
- American novelist another one dumped in the water
- Summon odd bits of beer and cake
Buddy explains!

The straight part
We know that "Sign/ to approach/stream" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case sign/ to approach/stream = beck.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 BECK mean?
BECK noun- A stream or small river.
- A significant nod, or motion of the head or hand, especially as a call or command.
- To nod or motion with the head.
- A vat.
- Anatomical uses.
- Figurative uses.
- Colloquial uses.