The most common and most likely answer to this crossword clue is the 5 letter word HOWDY
I've seen this crossword clue in The Guardian
H
O
W
D
Y
More clues leading to the result HOWDY
Buddy explains!

The straight part
We know that "Welcome" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case welcome = howdy.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 HOWDY mean?
HOWDY noun- A wife, a midwife.
- To greet informally, especially by saying "howdy"
- An informal greeting used in the South of the USA.