In favour of light weight computer file (7)
I believe the answer is:
program
'computer file' is the definition.
'program' can be an answer for 'file' (thesaurus). I'm not certain of the 'computer' bit.
'in favour of light weight' is the wordplay.
'in favour of' becomes 'pro' (being pro a particular cause).
'light weight' becomes 'gram' (I've seen this in another clue).
'pro'+'gram'='PROGRAM'
Can you help me to learn more?
(Other definitions for program that I've seen before include "system of instructions" , "Code" , "Instructions for PC, say" , "Set of computer instructions" , "Sequence of instructions to a computer" .)