The most common and most likely answer to this crossword clue is the 9 letter word SHELTERED
I've seen this crossword clue in Financial Times
S
H
E
L
T
E
R
E
D
More clues leading to the result SHELTERED
- The elders reconvened in a place of refuge
- Protected sheepdog, not one of bright colour
- Protected her eldest, snarling
- Protected Theresa deal, but not as planned
- Her eldest becomes reclusive
- Yet civilians lived such a life in the war
- Herd suffering with sleet to be put in barn?
- Covered empty loft before going into outhouse
- Offered protection, the woman left note, apparently ashamed
- Secluded trees held nuts
Buddy explains!

The straight part
We know that "reclusive" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case reclusive = sheltered.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 SHELTERED mean?
SHELTERED verb- To provide cover from damage or harassment; to shield; to protect.
- To take cover.
- Protected, as from wind or weather.
- (Of a person) who grew up being overprotected by parents or other guardians; often implies a lack of social skills, worldly experience, etc.