Under first of Rembrandts, I place false copy (7)
I believe the answer is:
replica
'copy' is the definition.
(replica is a kind of copy)
'under first of rembrandts i place false' is the wordplay.
'under' means one lot of letters go next to another.
'first of' suggests taking the first letters.
'false' indicates an anagram.
The first letter of 'rembrandts' is 'r'.
'i'+'place'='iplace'
'iplace' with letters rearranged gives 'eplica'.
'r' put next to 'eplica' is 'REPLICA'.
(Other definitions for replica that I've seen before include "Exact copy or model" , "Perfect copy" , "Reproduction, exact copy" , "Parcel I made into an exact copy" , "Exact copy as of sport trophy" .)