Evaluate certain amount (7)
I believe the answer is:
measure
'evaluate certain amount' is the definition.
'measure' can be an answer for 'evaluate' (synonyms). I'm unsure of the 'certain amount' bit.
'evaluate certain' is the wordplay.
'evaluate' becomes 'mea' (I am not sure about this - if you are sure you should believe this answer much more).
'certain' becomes 'sure' (synonyms).
'mea'+'sure'='MEASURE'
Can you help me to learn more?
(Other definitions for measure that I've seen before include "Assess length or height" , "Standard unit; dance" , "of specified size" , "So much" , "Ascertain the length etc." .)