Acclaim part of speech picked up by military engineers (6)
I believe the answer is:
renown
'acclaim' is the definition.
(thesaurus)
'part of speech picked up by military engineers' is the wordplay.
'part of speech' becomes 'noun' (noun is a kind of part of speech).
'picked up' shows a homophone (sound like).
'by' means one lot of letters go next to another.
'military engineers' becomes 'RE' (Royal Engineers in the British Army).
'noun' sounds like 'nown'.
'nown' after 're' is 'RENOWN'.
(Other definitions for renown that I've seen before include "Good reputation" , "Fame and public acclamation" , "Fame and eminence" , "Fame, respect" , "Celebrity, fame" .)