A colourful goddess to have in one's sight. (4)
I believe the answer is:
iris
'a colourful goddess' is the definition.
'iris' can be an answer for 'goddess' (Greek goddess of the rainbow). I am unsure of the 'a colourful' bit.
'in one's sight' is the wordplay.
'in' is an insertion indicator.
'one's' becomes 'I's' (Roman numeral).
'sight' becomes 'ri' (I can't explain this - if you can you should give a lot more credence to this answer).
'is' going around 'ri' is 'IRIS'.
'to have' acts as a link.
Can you help me to learn more?
(Other definitions for iris that I've seen before include "Pupil's place?" , "Plant - part of the eye" , "Part of the eye, usually brown or blue" , "Greek goddess of the rainbow" , "Flower - girl's name" .)