Possible Clues:

• Military Cross received by hard-line, versatile unit?
• Versatile building block of life
• Versatile part of body to check some cellulite
• Hold back group of spies finding modern research subject
• It's a function to generate specialised derivatives by differentiation
• Subject of recent medical research
• Stop undercover group producing biological germ
• Undifferentiated functional unit in an organism
• Biological building block
• Subject of medical research yet to have host almost replacing heart