Theatrical mechanical instrument trimmed in iron (5)
I believe the answer is:
flute
'theatrical mechanical' is the definition.
I can't judge whether this definition defines the answer.
'instrument trimmed in iron' is the wordplay.
'instrument' becomes 'lute' (lute is a kind of instrument).
'trimmed' means to remove the last letter (the last letter is trimmed off).
'in' is an insertion indicator.
'iron' becomes 'Fe' (chemical symbol for iron).
'lute' with its last letter taken off is 'lut'.
'lut' placed into 'fe' is 'FLUTE'.
Can you help me to learn more?
(Other definitions for flute that I've seen before include "High-pitched woodwind instrument" , "Blown" , "Wine glass; instrument" , "Musical instrument - wineglass" , "Narrow wineglass" .)