'Podgy' (mostly fat) servicemen getting starter of hamburgers (7)
I believe the answer is:
largish
'podgy' is the definition.
'mostly fat servicemen getting starter of hamburgers' is the wordplay.
'mostly' means to remove the last letter.
'fat' becomes 'lard' (lard is a kind of fat).
'servicemen' becomes 'gis' (plural of GI - private US soldier).
'getting' says to put letters next to each other.
'starter of' says to take the initial letters.
The initial letter of 'hamburgers' is 'h'.
'lard' with its last letter taken off is 'lar'.
'lar'+'gis'+'h'='LARGISH'
(Other definitions for largish that I've seen before include "Somewhat hefty" , "quite generous" , "Fairly big" , "sizeable proportions" , "Comfortable shoe" .)