Point to it again, this chemical (5)
I believe the answer is:
nitre
'chemical' is the definition.
(I've seen this before)
'point to it again' is the wordplay.
'point' becomes 'n' (North).
'to' means one lot of letters go next to another.
'again' becomes 're' (prefix meaning 'again').
'n'+'it'+'re'='NITRE'
'this' acts as a link.
(Other definitions for nitre that I've seen before include "Inert kind of saltpetre" , "Chemical" , "found in a slow match?" , "Gunpowder ingredient" , "constituent of gunpowder" .)