A long time to get salary topped (4)
I believe the answer is:
ages
'a long' is the definition.
(thesaurus)
'time to get salary topped' is the wordplay.
'time' becomes 'age' (age is a kind of time**).
'to get' says to put letters next to each other.
'topped' suggests taking the first letters.
The first letter of 'salary' is 's'.
'age'+'s'='AGES'
(Other definitions for ages that I've seen before include "Grows old like sage" , "Long periods" , "... of Man, according to WB Yeats" , "Rock of - - (hymn)" , "Yonks" .)