The most common and most likely answer to this crossword clue is the 5 letter word MOORS
I've seen this crossword clue in Financial Times
M
O
O
R
S
More clues leading to the result MOORS
Buddy explains!

The straight part
We know that "Iberian invaders/desolate areas" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case iberian invaders/desolate areas = moors.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 MOORS mean?
MOORS noun- An extensive waste covered with patches of heath, and having a poor, light soil, but sometimes marshy, and abounding in peat; a heath
- A game preserve consisting of moorland.
- To cast anchor or become fastened.
- To fix or secure (e.g. a vessel) in a particular place by casting anchor, or by fastening with ropes, cables or chains or the like
- To secure or fix firmly.