The most common and most likely answer to this crossword clue is the 4 letter word ANKH
I've seen this crossword clue in Independent
A
N
K
H
More clues leading to the result ANKH
- Cross but not completely thank heavens!
- Angry neighbour kicking hedge, initially cross
- Cross first part of fantastic city
- Cross during bank holiday
- Sign of life in bank – heavens!
- Cross tucked away by Tutankhamun, thank heavens – and Imran Khan
- Withdrawal from bank, Hatton Cross
- Thank heavens it contains sign of life!
- Symbol of life bank holiday reveals
- ‘Thank Heaven!’
Buddy explains!

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 ANKH mean?
ANKH noun- A cross shaped like a T with a loop at the top, the Egyptian hieroglyph representing the Egyptian triliteral ꜥnḫ and often used as an amulet or charm for this concept.
- Tau cross