Spreads content leaving bloggers' cycling thread on board (8)
I believe the answer is:
breadths
'spreads' is the definition.
(both can mean something's width)
'content leaving bloggers' cycling thread on board' is the wordplay.
'content leaving' means to remove the middle letters (the word's contents are removed).
'cycling' indicates an anagram.
'on board' is an insertion indicator.
'bloggers' with its middle taken out is 'bs'.
'thread' is an anagram of 'readth'.
'bs' going around 'readth' is 'BREADTHS'.
(Other definitions for breadths that I've seen before include "Widths" , "spreads" .)