Liven up green pants with one small bit of embellishment (8)

I believe the answer is:

energise

I'm a little stuck... Click here to teach me more about this clue!

'liven up' is the definition.
'energise' can be an answer for 'liven' ('liven'->'energize' is in my internal thesaurus and 'ize'->'ise'). I am unsure of the 'up' bit.

'green pants with one small bit of embellishment' is the wordplay.
'pants with' indicates an anagram (UK informal term for 'nonsense' or 'rubbish').
'one' becomes 'i' (Roman numeral).
'small' becomes 's' (abbreviation - e.g. clothes size).
'bit of' suggests taking the first letters.
The first letter of 'embellishment' is 'e'.
'green' mixed up with 'i' gives 'energi'.
'energi'+'s'+'e'='ENERGISE'

Can you help me to learn more?

(Other definitions for energise that I've seen before include "Give vitality to" , "To banish inertia" , "Motivate" , "Give active force" , "Give power to" .)

I've seen this clue in The Independent.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.