Lizard finally feeling all right about crossing City area (5)
I believe the answer is:
gecko
'lizard' is the definition.
(gecko is a kind of lizard)
'finally feeling all right about crossing city area' is the wordplay.
'finally' says to take the final letters.
'all right' becomes 'ok' (synonyms).
'about' is a reversal indicator.
'crossing' means one lot of letters goes inside another.
'city area' becomes 'EC' (EC is a London postcode area).
The last letter of 'feeling' is 'g'.
'ok' back-to-front is 'ko'.
'g'+'ko'='gko'
'gko' enclosing 'ec' is 'GECKO'.
(Other definitions for gecko that I've seen before include "Lizard with adhesive toes" , "Cold-blooded creature" , "Lizard than can't blink" , "Nocturnal lizard" , "Small lizard with adhesive foot-pads" .)