Sluggish porter loses zero time (7)
I believe the answer is:
dormant
'sluggish' is the definition.
(I've seen this before)
'porter loses zero time' is the wordplay.
'porter' becomes 'doorman' (synonyms).
'loses' suggests deleting specific letters.
'zero' becomes 'O' (O resembles 0).
'time' becomes 't' (abbreviation).
'doorman' with 'o' removed is 'dorman'.
'dorman'+'t'='DORMANT'
(Other definitions for dormant that I've seen before include "Hibernating" , "Deeply sleeping" , "In deep sleep" , "Latent" , "Inactive, but not dead" .)