Entrance to shopping arcade is narrow (5)
I believe the answer is:
small
'is narrow' is the definition.
(similar in meaning)
'entrance to shopping arcade' is the wordplay.
'entrance to' suggests taking the first letters.
'arcade' becomes 'mall' (I've seen this in another clue).
The first letter of 'shopping' is 's'.
's'+'mall'='SMALL'
(Other definitions for small that I've seen before include "Undersized" , "Limited in size or scope" , "tiddly" , "Petite" , "Young; modest" .)