Satisfied, once more, by a certain measure (5)
I believe the answer is:
metre
'a certain measure' is the definition.
'metre' can be an answer for 'measure' (metre is a kind of measure). I'm not sure about the 'a certain' bit.
'satisfied once more by' is the wordplay.
'satisfied' becomes 'met' (as in 'met the conditions of his contract').
'once more' becomes 're' (prefix in words like 're-emerge' or 're-enter').
'by' is a charade indicator (letters next to each other).
'met'+'re'='METRE'
Can you help me to learn more?
(Other definitions for metre that I've seen before include "Rhythmic arrangement of syllables in verse" , "100cm" , "39.37 inches" , "Approximately 39 inches" , "Distance" .)