What animal, entering flat, turning up in squalid place? (8)
I believe the answer is:
dungheap
'squalid place?' is the definition.
'what animal entering flat turning up' is the wordplay.
'what' becomes 'eh' (I've seen this in other clues).
'animal' becomes 'gnu' (I've seen this before).
'entering' indicates putting letters inside.
'flat' becomes 'pad' (a person's home).
'turning up' is a reversal indicator.
'eh'+'gnu'='ehgnu'
'ehgnu' placed into 'pad' is 'paehgnud'.
'paehgnud' in reverse letter order is 'DUNGHEAP'.
'in' is the link.
(Another definition for dungheap that I've seen is " mucky pile?".)