Follow one colleague possessing sex appeal (7)
I believe the answer is:
imitate
'follow' is the definition.
(I've seen this before)
'one colleague possessing sex appeal' is the wordplay.
'one' becomes 'i' (Roman numeral).
'colleague' becomes 'mate'.
'possessing' indicates putting letters inside.
'sex appeal' becomes 'it'.
'mate' enclosing 'it' is 'mitate'.
'i'+'mitate'='IMITATE'
(Other definitions for imitate that I've seen before include "Copy or mimic" , "I ate Tim! (anag.)" , "Reproduce" , "Copy someone" , "Mimic or follow as a model" .)