Optical device with soft rims, possibly (5)
I believe the answer is:
prism
'optical device' is the definition.
(prism is a kind of optical device)
'with soft rims possibly' is the wordplay.
'with' is an insertion indicator.
'soft' becomes 'p' (musical abbreviation for 'piano'**).
'possibly' is an anagram indicator.
'rims' with letters rearranged gives 'rism'.
'p' going inside 'rism' is 'PRISM'.
(Other definitions for prism that I've seen before include "Theatrical Miss" , "Triangular piece of glass, optical device" , "Type of polyhedron" , "Triangular shape of glass or quartz, breaks up a beam" , "Crystal form" .)