Nervous as second tyrant initially telephoned (6,2)

I believe the answer is:
strung up
'nervous' is the definition.
The answer and definition are different parts of speech. However, past participle verbs and adjectives sometimes define each other.
'second tyrant initially telephoned' is the wordplay.
I cannot really understand how this works, but
'second' could be 's' (common abbreviation) and 's' is found within the answer.
'telephoned' could be 'rung' (I've seen this before) and 'rung' is found in the answer.
The remaining letters 'tup' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
'as' is the link.
Can you help me to learn more?
(Other definitions for strung up that I've seen before include "Extremely tense - hanged" , "Tense, nervous" .)
