Mother clothes a decent man in purple (7)
I believe the answer is:
magenta
'purple' is the definition.
(I have seen 'Reddish purple' mean 'magenta' so perhaps 'purple' could also mean 'magenta')
'mother clothes a decent man' is the wordplay.
'mother' becomes 'ma' (ma can mean mother).
'clothes' means one lot of letters goes inside another (some letters clothe or cover others).
'decent man' becomes 'gent' (gent is a kind of man. I am not sure about the 'decent' bit.).
'a'+'gent'='agent'
'ma' enclosing 'agent' is 'MAGENTA'.
'in' acts as a link.
Can you help me to learn more?
(Other definitions for magenta that I've seen before include "Colour named after a bloody 1859 battle in Italy" , "Light purplish-red" , "Purplish-red - battle" , "this might be an ink" , "French victory" .)