Not the first pointer in such a tight space (6)
I believe the answer is:
narrow
'such a tight space' is the definition.
I can't judge whether this definition defines the answer.
'not the first pointer' is the wordplay.
'the first' indicates taking the first letters.
'pointer' becomes 'arrow' ('arrow' can be a synonym of 'pointer').
The first letter of 'not' is 'n'.
'n'+'arrow'='NARROW'
'in' acts as a link.
(Other definitions for narrow that I've seen before include "contract" , "Keen" , "Small in breadth" , "lacks vision" , "with not much room to spare" .)