Fundamental computer language (5)
I believe the answer is:
basic
I believe this is a double definition.
'fundamental' is the first definition.
('basic' can be similar in meaning to 'fundamental')
'computer language' is the second definition.
(I've seen this before)
(Other definitions for basic that I've seen before include "Fundamental, forming a starting-point" , "Fundamental -- early computer language" , "Elemental" , "At the simplest level" , "Radical" .)