While gaining ground previously (2,7)
I believe the answer is:
in advance
'previously' is the definition.
Both the answer and definition are adverbs. Perhaps they are linked in a way I don't understand?
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for in advance that I've seen before include "early" , "Beforehand - can invade accordingly (2.7)" , "Before the event" , "Ahead in place or time" .)