Bird falls on rodent with energy to test strength (7)
I believe the answer is:
titrate
'to test strength' is the definition.
I can't judge whether this defines the answer.
'bird falls on rodent with energy' is the wordplay.
'bird falls on' becomes 'tit' (I can't justify this - if you can you should believe this answer much more).
'rodent' becomes 'rat' (rat is a kind of rodent).
'with' is a charade indicator (letters next to each other).
'energy' becomes 'e' (physics symbol as in E=mci).
'tit'+'rat'+'e'='TITRATE'
Can you help me to learn more?
(Other definitions for titrate that I've seen before include "Measure the strength of (a solution) using a reagent" , "Determine strength of solution (chem.)" , "measure volume" , "Experimental way to measure" , "Use indicator maybe" .)