Merge Two Fields in SOLR

[EXTERNAL Taminidi Ravi (ETI, AA-AS/PAS-PTS)]

Hi Group,

I am not sure if we have any easy way to merge two  fields data in One Field, 
the Copy field doesn’t works as it stores as Multivalued.

Can someone suggest any workaround to achieve this Use Case?

FirstName:ABC
SurName:XYZ

I need an Another Field with Name:ABCXYZ where I have to do at SOLR END.. as 
the Source Data is read only and no control to comibine.


Thanks

Ravi