Sign agreement to save space significantly (2,3)
I believe the answer is:
no end
'significantly' is the definition.
Both the answer and definition are adverbs. Perhaps there's a link between them I don't understand?
'sign agreement to save space' is the wordplay.
'sign agreement' becomes 'nod' (I've seen this before).
'to save' means one lot of letters goes inside another.
'space' becomes 'en' (in printing, a space as wide as a letter 'n').
'nod' going around 'en' is 'NO END'.
Can you help me to learn more?
(Other definitions for no end that I've seen before include "Without limit" , "Non-stop" , "A lot" , "Very much (colloq.)" , "detailed?" .)