Perhaps fragmentary portrait is of prophet (6)
I believe the answer is:
mosaic
This could be a double definition.
'perhaps fragmentary portrait' is the first definition.
The answer and definition can be both man-made objects as well as being singular nouns.
Maybe there's an association between them I don't understand?
'of prophet' is the second definition.
The definition suggests a singular noun which matches the answer.
'is' is the link.
Can you help me to learn more?
(Other definitions for mosaic that I've seen before include "Relating to Moses" , "Design made of small pieces of coloured stone or glass" , "Like the Commandments" , "Inlaid work - of a Hebrew prophet" , "Design of many small pieces" .)