It facilitates travel when a girl goes to South Africa (4)
I believe the answer is:
visa
'it facilitates travel' is the definition.
The definition suggests a singular noun which matches the answer.
'a girl goes to south africa' is the wordplay.
'a girl' becomes 'vi' (short for Violet).
'goes to' says to put letters next to each other.
'south africa' becomes 'SA' (abbreviation).
'vi'+'sa'='VISA'
'when' is the link.
Can you help me to learn more?
(Other definitions for visa that I've seen before include "Stamp affixed to passport as permission to enter country" , "Travel permit stamped in passport etc" , "travel authority" , "It allows the bearer to enter the country issuing it" , "Mark on passport" .)