Read start of testimony that is barely sufficient (5)
I believe the answer is:
scant
'is barely sufficient' is the definition.
(I've seen this before)
'read start of testimony' is the wordplay.
'read' becomes 'scan' (scanning is a kind of reading).
'start of' suggests taking the first letters.
The first letter of 'testimony' is 't'.
'scan'+'t'='SCANT'
'that' acts as a link.
(Other definitions for scant that I've seen before include "Bare" , "Barely sufficient" , "Limited, inadequate" , "Less than the required amount" , "Deficient, sparing" .)