Nook in which it's nice to be out of breath? (5)
I believe the answer is:
niche
'nook' is the definition.
(I've seen this before)
'it's nice to be out of breath?' is the wordplay.
'to be out' means to remove the last letter.
'of breath?' becomes 'he' (I can't justify this - if you can you should believe this answer much more).
'nice' with its final letter taken off is 'nic'.
'nic'+'he'='NICHE'
'in which' is the link.
Can you help me to learn more?
(Other definitions for niche that I've seen before include "Cosy corner?" , "Suitable spot" , "Specialised corner of the market" , "Cosy spot" , "Comfortable position" .)