A kind of tension (6)
I believe the answer is:
strain
I believe this clue is a double definition.
'a kind' is the first definition.
(thesaurus)
'tension' is the second definition.
(synonyms)
'of' acts as a link.
(Other definitions for strain that I've seen before include "Great effort - sieve" , "Pull (a muscle?)" , "Music" , "song" , "Stretch or exert to the utmost" .)