Experiencing CLR error on SQL Azure DB
While Azure SQL Database (not the new Managed Instance) does not support custom SQLCLR Assemblies (i.e. the "CLR enabled" server-level configuration option), CLR is still used internally for the following features:


CLR datatypes:


Geometry
Geography
Hierarchyid

Built-in functions:


introduced in SQL Server 2012:


FORMAT
PARSE
TRY_PARSE

introduced in SQL Server 2016:


AT TIME ZONE
COMPRESS
DECOMPRESS
sys.time_zone_info

maybe others

SSIS (Fuzzy Lookup / sp_FuzzyLookupTableMaintenanceInvoke, etc)
Change Data Capture (CDC)
Replication
Master Data Services
Policy Based Managemen (PBM; originally named "Dynamic Management Framework (DMF)" )
External Tables (including External Data Sources and possibly External File Formats): This functionality is new as of SQL Server 2016, and this functionality using CLR internally has been mentioned in other answers here by Joe and Henrik. Both Joe and Henrik indicate being told by Microsoft that External Tables rely upon CLR, and while I have not been able to confirm this directly (by seeing the system App Domain get created when using any of this functionality), I was at least able to confirm that when "Lightweight Pooling" mode is enabled, all 3 of these components fail with the following error:


  Msg 7432, Level 16, State 0, Line XXXXX
  Heterogeneous queries and use of OLEDB providers are not supported in fiber mode.

maybe others


Of course, this does not point to what would be hogging memory. But it should help identify the affected area(s).