Comfy on the bottom, chair for sunbathing topless is comparatively new (7)
I believe the answer is:
younger
'comparatively new' is the definition.
('young' can be similar in meaning to 'new')
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for younger that I've seen before include "Not so old" , "Seven PM" , "Less experienced" , "more boyish" , "Less mature" .)