An agreement over small car for the present time (4,6)
I believe the answer is:
anno domini
'the present time' is the definition.
Both the definition and answer are singular nouns.
Perhaps you can see an association between them that I don't see?
'an agreement over small car' is the wordplay.
'agreement' becomes 'nod' (a nod indicates agreement).
'over small' becomes 'o' (cricket abbreviation; 'small' asks for a short form).
'car' becomes 'mini' (Mini Cooper).
'an'+'nod'+'o'+'mini'='ANNO DOMINI'
'for' acts as a link.
Can you help me to learn more?
(Other definitions for anno domini that I've seen before include "In the year of our Lord" , "Advancing old age (informal)" , "later days" , "having a date, she may put it on" , "AD in full" .)