It is found in sun block although it's alien to some of us (7)
I believe the answer is:
visitor
'it is found in sun block although it's alien to some of us' is the definition.
The definition suggests a singular noun which matches the answer.
'it is found in sun block although it's' is the wordplay.
'it is found in' indicates putting letters inside.
'sun block although' becomes 'visor' (I can't explain this - if you can you should give a lot more credence to this answer).
'it's' becomes 'it' (I've seen this in other clues).
'visor' placed around 'it' is 'VISITOR'.
Can you help me to learn more?
(Other definitions for visitor that I've seen before include "One coming to call" , "Seasonal migratory bird" , "Guest - tourist" , "Someone calling (again at 23?)" , "Person turning up" .)