Silk was an observer at the meeting (5)
I believe the answer is:
satin
'silk' is the definition.
(I've seen this before)
'an observer at the meeting' is the wordplay.
'an observer' becomes 'sat' (I am not sure about this - if you are sure you should believe this answer much more).
'at' becomes 'in' (synonymous in some cases - eg at school, in school).
'the meeting' says to put letters next to each other.
'sat'+'in'='SATIN'
'was' is the link.
Can you help me to learn more?
(Other definitions for satin that I've seen before include "Stain on silky cloth" , "Rich cloth" , "Lustrous fabric" , "Silky material" , "covered with?" .)