Heartlessly welcome a boast about love for actress (5,5)
I believe the answer is:
greta garbo
'for actress' is the definition.
(I've seen this before)
'heartlessly welcome a boast about' is the wordplay.
'heartlessly' means to remove the middle letters.
'welcome' becomes 'greet' (to greet someone is to welcome them).
'boast about' becomes 'garbo' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'greet' with its middle taken out is 'gret'.
'gret'+'a'+'garbo'='GRETA GARBO'
'love' is the link.
This may not be right. It may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for greta garbo that I've seen before include "Old actress" , "See actress" .)