Work out one approach, lacking information (8)
I believe the answer is:
untangle
'work out' is the definition.
(thesaurus)
'one approach lacking information' is the wordplay.
I cannot really see how this works, but
'one' could be 'un' (northern English dialect form of 'one') and 'un' is found in the answer.
'approach' could be 'angle' (as in a journalist's approach to a story) and 'angle' is found within the answer.
A single letter 't' remains which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for untangle that I've seen before include "Make free from disorder" , "Make free from confusion" , "Extricate" , "'Unpick, unravel (8)'" , "Straighten out, free from mesh" .)