Make subsequent addition, if retort worked (8)
I believe the answer is:
retrofit
'make subsequent addition if retort worked' is the definition.
I can't judge whether this defines the answer.
'if retort worked' is the wordplay.
'worked' is an anagram indicator.
'if'+'retort'='ifretort'
'ifretort' anagrammed gives 'RETROFIT'.
Can you help me to learn more?
(Other definitions for retrofit that I've seen before include "Make later modifications to (equipment, etc)" , "Add (component) not originally in place" , "Add (a component) not in the original build" , "Belatedly modify" , "make change after delivery" .)