What the captain did to a row of soldiers was annoying (7)
I believe the answer is:
rankled
'annoying' is the definition.
The answer and definition are not the same part of speech. However, past participle verbs and adjectives sometimes mean the same thing.
'what the captain did to a row of soldiers' is the wordplay.
I cannot really see how this works, but
'did' could be 'led' (leading is a kind of doing) and 'led' is located in the answer.
'a' could be 'an' and 'an' is located in the answer.
This explanation may well be incorrect...
'was' acts as a link.
Can you help me to learn more?
(Other definitions for rankled that I've seen before include "Embittered" , "Caused lasting resentment and bitterness" , "Caused ongoing annoyance" , "caused constant annoyance" , "Festered" .)