Obsessive sibling admitting yen for dissection (8)
I believe the answer is:
analysis
'dissection' is the definition.
(I've seen this before)
'obsessive sibling admitting yen' is the wordplay.
'obsessive' becomes 'anal' (I've seen this before).
'sibling' becomes 'sis' (I have seen 'Little sibling ' mean 'sis' so perhaps 'sibling' could also mean 'sis').
'admitting' means one lot of letters goes inside another.
'yen' becomes 'y'.
'anal'+'sis'='analsis'
'analsis' going around 'y' is 'ANALYSIS'.
'for' is the link.
(Other definitions for analysis that I've seen before include "Examination to determine component parts" , "Examination of structure of problem" , "Dissection and examination" , "Detailed breakdown" , "Study of mind" .)