Tuck in before we get growth (6)
I believe the answer is:
crease
'tuck' is the definition.
(thesaurus)
I don't understand the rest of the clue.
(Other definitions for crease that I've seen before include "Line produced by folding" , "Folded line" , "Furrow, wrinkle" , "Mark made by fold" , "Cricket line; wrinkle" .)