Anxious to be perfect perhaps (5)
I believe the answer is:
tense
This clue is a double definition.
'anxious' is the first definition.
(I've seen this in another clue)
'be perfect perhaps' is the second definition.
(eg past perfect tense)
'to' is the link.
(Other definitions for tense that I've seen before include "Verb form, indicates time" , "Maybe past" , "Attribute of verbs signalling time" , "Rigid; verb form" , "Subject to strain" .)