Rope three initially then another three (6)
I believe the answer is:
tether
'rope' is the definition.
(thesaurus)
'three initially then another three' is the wordplay.
'initially' says to take the initial letters.
'then' means one lot of letters go next to another.
'another' indicates an anagram.
The first letter of 'three' is 't'.
'three' anagrammed gives 'ether'.
't'+'ether'='TETHER'
(Other definitions for tether that I've seen before include "End of ones --" , "Rope holding an animal" , "Halter" , "Rope for tying animal" , "Tie with rope or chain" .)