Hardworking animal in front of one couple and us (9)
I believe the answer is:
assiduous
'hardworking' is the definition.
(thesaurus)
'animal in front of one couple and us' is the wordplay.
'animal' becomes 'ass' (I've seen this before).
'front of' indicates taking the first letters.
'one couple' becomes 'duo' (synonyms).
'and' says to put letters next to each other.
The initial letter of 'in' is 'i'.
'ass'+'i'+'duo'+'us'='ASSIDUOUS'
(Other definitions for assiduous that I've seen before include "Showing great care and perseverance" , "Persevering" , "Hard-working" , "Marked by care and persistent effort" , "Diligent" .)