Pondered how many were employed (5)
I believe the answer is:
mused
'pondered' is the definition.
('muse' can be a synonym of 'ponder')
'many were employed' is the wordplay.
I cannot quite see how this works, but
'many' could be 'm' (Roman numeral for a thousand) and 'm' is found in the answer.
'employed' could be 'used' ('use' can be a synonym of 'employ') and 'used' is present in the answer.
No letters remain.
This explanation may well be incorrect...
'how' is the link.
Can you help me to learn more?
(Other definitions for mused that I've seen before include "Closer" , "Was absorbed in thought" , "Reflected or pondered" , "Reflected in silence" , "Thought (to oneself)" .)