Ridge where one hundred take breather (5)
I believe the answer is:
crest
'ridge' is the definition.
(I've seen this before)
'one hundred take breather' is the wordplay.
'one hundred' becomes 'c' (Roman numeral).
'take' says to put letters next to each other.
'breather' becomes 'rest' (a breather is a break or rest).
'c'+'rest'='CREST'
'where' is the link.
(Other definitions for crest that I've seen before include "Heraldic device representing a family" , "Top of a ridge/wave" , "Highest point" , "Tuft" , "Top point of hill or wave" .)