Recorded about engineers having got thinner (7)
I believe the answer is:
tapered
'got thinner' is the definition.
The definition and answer can be both related to change as well as being past participle verbs.
Perhaps there's an association between them I don't understand?
'recorded about engineers' is the wordplay.
'recorded' becomes 'taped' ('tape' can be a synonym of 'record').
'about' means one lot of letters goes inside another.
'engineers' becomes 're' (Royal Engineers).
'taped' placed around 're' is 'TAPERED'.
'having' acts as a link.
Can you help me to learn more?
(Other definitions for tapered that I've seen before include "Pointed" , "came to the point" , "With thickness reduced towards an end" , "Narrowed by red tape" , "Getting smaller towards the end" .)