Tense show, faultless (7,7)
I believe the answer is:
present perfect
'tense' is the definition.
(present perfect is a grammatical tense)
'show faultless' is the wordplay.
'show' becomes 'present' (presenting is a kind of showing).
'faultless' becomes 'perfect' (similar in meaning).
'present'+'perfect'='PRESENT PERFECT'
(Other definitions for present perfect that I've seen before include "writing the briefest of thank you letters?" , "giver is happy to hear this?" , "Tense" , "I have left in this?" .)