Around countryside I ran, certainly ambling initially (5)
I believe the answer is:
circa
'around' is the definition.
(circa means around or approximately)
'countryside i ran certainly ambling initially' is the wordplay.
'countryside i' becomes 'ci' (this could be a standard abbreviation of which I'm unaware).
'initially' says to take the initial letters.
The initial letters of 'ran certainly ambling' is 'rca'.
'ci'+'rca'='CIRCA'
Can you help me to learn more?
(Other definitions for circa that I've seen before include "Approximately (Latin)" , "Preposition meaning about, usually preceding a date" , "Costa del Sol city" , "(Especially of a date) approximately" , "Roughly" .)