Information held by a Cyprus bureau (6)
I believe the answer is:
agency
'bureau' is the definition.
('agency' can be a synonym of 'bureau')
'information held by a cyprus' is the wordplay.
'information' becomes 'gen' (gen is a kind of information).
'held by' means one lot of letters goes inside another.
'cyprus' becomes 'cy' (abbreviation).
'a'+'cy'='acy'
'gen' going into 'acy' is 'AGENCY'.
(Other definitions for agency that I've seen before include "Cagney (anag.)" , "Office or business of one who does business for others" , "Employment bureau" , "Organisation; intervention" , "Bureau; action" .)