Rep welcomed by chap almost purplish red (7)
I believe the answer is:
magenta
'purplish red' is the definition.
(I've seen this before)
'rep welcomed by chap almost' is the wordplay.
'rep' becomes 'agent' (I've seen this before).
'welcomed by' indicates putting letters inside (I've seen this in other clues).
'chap' becomes 'man' (I've seen this before).
'almost' means to remove the last letter (most of the word but not all of it).
'man' with its last letter removed is 'ma'.
'agent' inserted within 'ma' is 'MAGENTA'.
(Other definitions for magenta that I've seen before include "French victory" , "Shade of purple" , "A crimson dye" , "Light purplish-red" , "Colour named after a bloody 1859 battle in Italy" .)