The most common and most likely answer to this crossword clue is the 9 letter word ANCHORAGE
I've seen this crossword clue in The Times
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More clues leading to the result ANCHORAGE
- A new unexciting job collecting silver as a source of security
- A number show anger outside church in American port
- A random charge on port
- US city gets a new church — with nothing to go up the wall
- Change oar going round the harbour
- Ache and groan wandering around city abroad
- Change oar arrangement to reach harbour
- Silver in an assignment for city
- Criminal on a charge in Alaskan port
- A new job guarding silver in harbour
Buddy explains!

The straight part
We know that "a source of security" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case a source of security = anchorage.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 ANCHORAGE mean?
ANCHORAGE noun- A harbor, river, or offshore area that can accommodate a ship at anchor, either for quarantine, queuing, or discharge..
- A fee charged for anchoring.
- That into which something is anchored or fastened.
- The surgical fixation of prolapsed organs.
- The act of anchoring, or the condition of lying at anchor.
- The set of anchors belonging to a ship.
- The retreat of a hermit, or anchorite.
- Something on which one may depend for security; ground of trust.