Military display is beginning to trouble needleworker (9)
I believe the answer is:
tattooist
'trouble needleworker' is the definition.
The definition suggests a singular noun which matches the answer.
'military display is beginning to' is the wordplay.
'military display' becomes 'tattoo' (I've seen this before).
'beginning' says to take the initial letters.
The initial letter of 'to' is 't'.
'tattoo'+'is'+'t'='TATTOOIST'
Can you help me to learn more?
(Other definitions for tattooist that I've seen before include "Skin decorator" , "Designer" , "permanent marker?" , "Sort of marksman" , "Skin artist" .)