I believe in having colour in the house (5)
I believe the answer is:
credo
'i believe' is the definition.
(I've seen this before)
'colour in the house' is the wordplay.
'colour' becomes 'red' (red is a kind of colour).
'in' indicates putting letters inside.
'the house' becomes 'co' (I've seen this in other clues).
'red' inserted within 'co' is 'CREDO'.
'in having' acts as a link.
I am not very happy about this link. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for credo that I've seen before include "One's system of beliefs" , "System of principles" , "mission statement" , "Section of mass" , "Faith - I believe" .)