Review text concerning colour round first letter (6)
I believe the answer is:
reread
'review text' is the definition.
(read some text again)
'concerning colour round first letter' is the wordplay.
'concerning' becomes 're' (both can mean on a particular topic).
'colour' becomes 'red' (red is a kind of colour).
'round' is an insertion indicator.
'first letter' becomes 'a' (in the alphabet).
'red' going around 'a' is 'read'.
're'+'read'='REREAD'
(Other definitions for reread that I've seen before include "Give script second seeing to" , "Perused again" , "Peruse or scan again; it's dearer" , "Study text again" , "look again at manifesto?" .)