Methodically search quantity of data stored on firm (4)
I believe the answer is:
comb
'methodically search' is the definition.
'comb' can be an answer for 'search' (combing is a kind of searching). I am not sure about the 'methodically' bit.
'quantity of data stored on firm' is the wordplay.
I cannot really see how this works, but
'quantity' could be 'mb' (Mb is an example) and 'mb' is found within the answer.
'of' could be 'o' and 'o' is found within the answer.
A single letter 'c' remains which might be clued in a way I don't understand.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for comb that I've seen before include "Fowl's crest" , "Ransack, scour" , "Toothed instrument" , "Search well; bird's crest" , "Untangle (hair)" .)