To sleep in centre of city is not appropriate (5)
I believe the answer is:
inapt
'not appropriate' is the definition.
(I've seen this before)
'to sleep in centre of city' is the wordplay.
'to sleep' becomes 'nap' (napping is a kind of sleeping).
'in' is an insertion indicator.
'centre of' says to take the centre.
The middle of 'city' is 'it'.
'nap' going within 'it' is 'INAPT'.
'is' is the link.
(Other definitions for inapt that I've seen before include "Cartoon duck" , "It's clumsy" , "Unsuited" , "Useless" , "badly judged" .)