It adds colour to things (7)
I believe the answer is:
pigment
'it adds colour to things' is the definition.
The definition suggests a singular noun which matches the answer.
'it' is the wordplay.
I cannot quite see how this works, but
'it' could be 't' (abbreviation. e.g. in 'tis) and 't' is located in the answer.
The remaining letters 'pigmen' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for pigment that I've seen before include "Substance giving colour" , "become imbued" , "Colour or dye" , "Colourful substance" , "Colouring material" .)