Notice decay at edges, squalid (5)
I believe the answer is:
seedy
'squalid' is the definition.
(synonyms)
'notice decay at' is the wordplay.
'notice' becomes 'see' (I've seen this before).
'decay at' becomes 'dy' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'see'+'dy'='SEEDY'
'edges' acts as a link.
I am not very happy about this link. It may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for seedy that I've seen before include "Unpleasant" , "Pip is" , "Raspberry jam might be" , "Off-colour" , "Sordid, squalid" .)