Bright colour means a lot to soldiers (3)
I believe the answer is:
red
'bright colour' is the definition.
'red' can be an answer for 'colour' (red is a kind of colour). I'm not certain of the 'bright' bit.
'a lot to soldiers' is the wordplay.
'a lot' becomes 'd'.
'to' means one lot of letters go next to another (I've seen this in other clues).
'soldiers' becomes 're' (Royal Engineers).
'd' put after 're' is 'RED'.
'means' is the link.
Can you help me to learn more?
(Other definitions for red that I've seen before include "Left-wing" , "Colour for danger" , "Colour of 1 across" , "Colour of communism" , "'If you see it, perhaps you're angry (3)'" .)