License first person at work showing enthusiastic interest (7)
I believe the answer is:
passion
'enthusiastic interest' is the definition.
(passion can mean an intense interest)
'license first person at work' is the wordplay.
'license' becomes 'pass' (pass is a kind of license).
'first person' becomes 'I' (first-person pronoun).
'at work' becomes 'on' (on can mean activated or working).
'pass'+'i'+'on'='PASSION'
'showing' is the link.
(Other definitions for passion that I've seen before include "Ardour, fervour" , "Intense enthusiasm for something" , "Intense emotion, anger or love" , "Ardent love" , "Fervent love" .)