The most common and most likely answer to this crossword clue is the 6 letter word HERMIT
I've seen this crossword clue in The Guardian
H
E
R
M
I
T
More clues leading to the result HERMIT
- What widow would give not to end a recluse
- Small island near France – the very thing for someone demanding solitude
- Solitary lady’s time almost up
- That girl getting on with German in solitary
- One wanting solitude gets it on small Channel Island
- Mrs Romney’s man? They say he’s retired from public life
- Solitary island faces empty inlet
- Retiring sort of woman at [French] university
- Solitary religious person in that female university in US
- Anchorite in ruins of Mitre Hotel
Buddy explains!

The straight part
We know that "Solitary" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case solitary = hermit.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 HERMIT mean?
HERMIT noun- A religious recluse; someone who lives alone for religious reasons; an eremite.
- A recluse; someone who lives alone and shuns human companionship.
- A spiced cookie made with molasses, raisins, and nuts.
- A hermit crab.
- A hummingbird in the subfamily Phaethornithinae.