Like a party hat or fleece coat from Isaac (5)
I believe the answer is:
conic
'like a party hat' is the definition.
I can't judge whether this defines the answer.
'fleece coat from isaac' is the wordplay.
'fleece' becomes 'con' (I've seen this before).
'coat from isaac' becomes 'ic' (I can't explain this - if you can you should believe this answer much more).
'con'+'ic'='CONIC'
'or' is the link.
Can you help me to learn more?
(Other definitions for conic that I've seen before include "Shaped like an ice cream cornet" , "Tapering from a circle to a point" , "elliptical shape" , "With a tapering shape" , "Figure of circle, ellipse, parabola or hyperbola" .)