Turning up in front of small hotel, one may see this on the door (4)
I believe the answer is:
push
'one may see this on the door' is the definition.
The definition suggests a singular noun which matches the answer.
'turning up in front of small hotel' is the wordplay.
'turning' says the letters should be written in reverse.
'in front of' says to take the initial letters.
The initial letters of 'small hotel' is 'sh'.
'up' reversed gives 'pu'.
'pu'+'sh'='PUSH'
Can you help me to learn more?
(Other definitions for push that I've seen before include "Press forward" , "Force one's way (through)" , "Illegally supply" , "Propel forwards" , "Offensive - press" .)