Fix mast with friend by rear - a collector's item (5,5)
I believe the answer is:
stamp album
'rear a collector's item' is the definition.
The answer and definition can be both man-made objects as well as being singular nouns.
Maybe you can see a link between them that I can't see?
'fix mast with friend by' is the wordplay.
'fix' indicates an anagram.
'with' means one lot of letters go next to another.
'friend' becomes 'pal' (pal can mean a friend).
'by' becomes 'bum' (I can't justify this - if you can you should give a lot more credence to this answer).
'mast' is an anagram of 'stam'.
'stam'+'pal'+'bum'='STAMP-ALBUM'
Can you help me to learn more?
(Other definitions for stamp album that I've seen before include "collector's book" , "Something used by philatelists" , "Philatelist's book" .)