Continued to have a problem in the grass border (7)
I believe the answer is:
resumed
'continued' is the definition.
(resuming is a kind of continuing)
'a problem in the grass border' is the wordplay.
'a problem' becomes 'sum' (arithmetic problem).
'in the' is an insertion indicator.
'grass border' becomes 'reed' (I am not sure about this - if you are sure you should believe this answer much more).
'sum' going within 'reed' is 'RESUMED'.
'to have' is the link.
Can you help me to learn more?
(Other definitions for resumed that I've seen before include "Started again after a break" , "Recommenced" , "Once again picked up" , "Continued after a pause" , "Carried on again" .)