Allowing no breathing space (8)
I believe the answer is:
airtight
'allowing no breathing' is the definition.
I can't judge whether this definition defines the answer.
'space' is the wordplay.
I cannot quite see how this works, but
'space' could be 'air' (I've seen this in another clue) and 'air' is located in the answer.
The remaining letters 'tight' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for airtight that I've seen before include "not letting out a breath?" , "Totally sealed" , "Not allowing gas to enter or escape" , "(Of a defence) having no weaknesses" , "Impenetrable" .)