Two components have minor role (3,4)
I believe the answer is:
bit part
'minor role' is the definition.
(synonyms)
'two components' is the wordplay.
'two components' can mean two replacements for 'component'.
'component' becomes 'bit'.
'component' becomes 'part' (I've seen this before).
'bit'+'part'='BIT PART'
'have' is the link.
(Other definitions for bit part that I've seen before include "cameo" , "Tool" , "Very minor role" , "Small acting role" , "extra work, perhaps" .)