On the film credits, what the undernamed provided? (8)
I believe the answer is:
subtitle
'the undernamed provided?' is the definition.
I can't tell whether this defines the answer.
'on the film credits' is the wordplay.
'on' indicates putting letters inside (as in clothing 'on' a person).
'the film' becomes 'It'.
'credits' becomes 'subtle' (I can't explain this - if you can you should believe this answer much more).
'it' inserted into 'subtle' is 'SUBTITLE'.
'what' acts as a link.
Can you help me to learn more?
(Other definitions for subtitle that I've seen before include "Explanatory legend" , "small print?" , "Foreign dialogue translation shown on film" , "minor heading" , "A subordinate caption as under foreign film" .)