Stout men put up walls of lovely old college (4-4)
I believe the answer is:
roly-poly
'stout' is the definition.
(thesaurus)
'men put up walls of lovely old college' is the wordplay.
'men' becomes 'OR' (Other Ranks: non-commissioned soldiers).
'put up' is a reversal indicator.
'walls of' suggests removing the centre (the external letters or walls of the word are used).
'old college' becomes 'poly' (polytechnic).
'lovely' with its centre removed is 'ly'.
'or' in reverse letter order is 'ro'.
'ro'+'ly'+'poly'='ROLY-POLY'
(Other definitions for roly-poly that I've seen before include "Kind of cylindrical jam pudding" , "Desert pudding of suet and jam" , "Short and plump" , "Substantial" , "Plump in appearance- steamed pudding" .)