Calcutta prison: very attractive place? (5,4)
I believe the answer is:
black hole
'calcutta prison' is the definition.
'black hole' can be an answer for 'prison' (thesaurus). I am not certain of the 'calcutta' bit.
'very attractive place?' is the wordplay.
'very attractive' becomes 'black' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'place?' becomes 'hole' (I have seen 'Nasty place ' mean 'hole' so perhaps 'place' could also mean 'hole').
'black'+'hole'='BLACK HOLE'
Can you help me to learn more?
(Other definitions for black hole that I've seen before include "Space left after collapse of a star" , "object in 21 [SPACE] having very strong 20 [GRAVITY]" , "discovered in Calcutta" , "'Region of space from which nothing can escape (5,4)'" , "Astronomical curiosity" .)